Stabilization of hydroformylation catalysts based on phosphoramide ligands

ABSTRACT

The present invention relates to a process for the hydroformylation of ethylenically unsaturated compounds by reaction with carbon monoxide and hydrogen in the presence of a catalytically active fluid which comprises a dissolved metal complex of a metal of transition group VIII of the Periodic Table of the Elements with at least one phosphoramidite compound as ligand, wherein the fluid is brought into contact with a base.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a National Stage application ofPCT/EP2004/011886, filed Oct. 22, 2004, which claims priority fromGerman Patent Application No. DE 103 49 343.3, filed Oct. 23, 2003.

DESCRIPTION

The present invention relates to a process for the hydroformylation ofethylenically unsaturated compounds by reaction with carbon monoxide andhydrogen in the presence of a catalytically active fluid which comprisesa dissolved metal complex of a metal of transition group VIII of thePeriodic Table of the Elements with at least one phosphoramiditecompound as ligand, wherein the fluid is brought into contact with abase.

Hydroformylation or the oxo process is an important industrial processand is employed for preparing aldehydes from olefins, carbon monoxideand hydrogen. These aldehydes can, if desired, be hydrogenated by meansof hydrogen in the same process to give the corresponding oxo alcohols.The reaction itself is strongly exothermic and generally proceeds undersuperatmospheric pressure and at elevated temperatures in the presenceof catalysts. Catalysts used are Co, Rh, Ir, Ru, Pd or Pt compounds orcomplexes which may be modified by means of N- or P-containing ligandsto influence the activity and/or selectivity. In the hydroformylationreaction of olefins having more than two carbon atoms, the formation ofmixtures of isomeric aldehydes can occur due to the possible CO additiononto each of the two carbon atoms of a double bond. In addition, doublebond isomerization, i.e. a shift of internal double bonds to a terminalposition and vice versa, can also occur when using olefins having atleast four carbon atoms.

Owing to the significantly greater industrial importance of α-aldehydes,optimization of the hydroformylation catalysts to achieve a very highhydroformylation activity and at the same time a very low tendency toform olefins having double bonds which are not in the α position isdesirable. In addition, there is a need for hydroformylation catalystswhich lead to good yields of α- and in particular n-aldehydes even whenlinear internal olefins are used as starting materials. Here, thecatalyst has to make possible both the establishment of an equilibriumbetween internal and terminal double bond isomers and the very selectivehydroformylation of the terminal olefins.

WO 00/56451 describes hydroformylation catalysts based onphosphinamidite ligands in which the phosphorus atom together with anoxygen atom to which it is bound forms a 5- to 8-membered heterocycle.

WO 02/083695 describes chelating pnicogen compounds in which at leastone pyrrole group is bound via the pyrrole nitrogen to each of pnicogenatoms. These chelating pnicogen compounds are suitable as ligands forhydroformylation catalysts.

WO 03/018192 describes, inter alia, pyrrole-phosphorus compounds inwhich at least one pyrrole group which is substituted and/or integratedinto a fused ring system is covalently bound via its pyrrole nitrogen tothe phosphorus atom, which display a very good stability when used asligands in hydroformylation catalysts.

The German patent application 102 43 138.8, which is not a priorpublication, describes pnicogen compounds which have two pnicogen atomsand in which pyrrole groups can be bound via a pyrrole nitrogen to bothpnicogen atoms and both pnicogen atoms are bound via a methylene groupto a bridging group. These pnicogen compounds are suitable as ligandsfor hydroformylation catalysts.

The abovementioned catalysts display a high regioselectivity to terminalproduct aldehydes both in the hydroformylation of α-olefins and in thehydroformylation of internal linear olefins. In addition, they have agood stability under the hydroformylation conditions, particularly inthe case of hydroformylation catalysts based on ligands in which one ormore 3-alkylindole group(s) is/are bound to the phosphorus atom.Nevertheless, additional stabilization is desirable with a view to thelong catalyst lives required for large-scale industrial use.

DE-A-102 06 697 describes a hydroformylation process which makes itpossible for the products of value to be separated off and the catalystto be recirculated with a very low loss of activity. This is achievedusing a hydroformylation catalyst based on a bidentate phosphine ligandwhich is stabilized by at least one monodentate phosphine ligand.

EP-A-0 149 894 and U.S. Pat. No. 4,567,306 describe a continuoushydroformylation process using a hydroformylation catalyst which has acyclic phosphite having a phosphorus atom as bridge head as ligand.Three oxygen atoms are bound directly to the phosphorus atom and atleast two of these form a ring together with the phosphorus atom.Suitable ligands have, for example, a phosphabicyclo[2.2.2]octane orphosphaadamantyl skeleton. The process includes the stabilization of theligands by means of a tertiary amine.

EP-A-0 155 508 and U.S. Pat. No. 4,599,206 describe hydroformylationprocesses using catalyst complexes based on diorganophosphite ligands,in which a liquid output can be taken from the reaction zone, broughtinto contact with a weak base anion exchanger and subsequently returnedto the reaction zone. U.S. Pat. No. 4,717,775 describes a variant of thehydroformylation process disclosed in the abovementioned documents,according to which the hydroformylation is carried out in the presenceof free diorganophosphite ligand. U.S. Pat. No. 4,774,361 describes aprocess for avoiding or minimizing the precipitation of rhodium fromrhodium-phosphite catalyst complexes in a hydroformylation processhaving a liquid circuit, in which the aldehyde is distilled off from thereaction mixture and this distillation is carried out in the presence ofan organic polymer containing at least three polar amide functions, forexample polyvinylpyrrolidone or copolymers of vinylpyrrolidone and vinylacetate. EP-A-0 276 231 has a disclosure content comparable to U.S. Pat.No. 4,774,361.

EP-A-214 622 describes a hydroformylation process using a catalyst basedon a polyphosphite ligand which has from two to six phosphite groups. Itis stated that the polyphosphite ligands can be stabilized if necessaryby bringing the liquid output from the reaction zone into contact with aweak base anion-exchange resin before or after the product aldehydeshave been separated off and only then recirculating the stream to thehydroformylation reactor.

WO 97/20794 and U.S. Pat. No. 5,741,942 describe methods of separatingacidic phosphorus compounds from a reaction liquid comprising ametal-organophosphite catalyst complex and, if desired, freeorganophosphite ligands by treating the reaction liquid with an aqueousbuffer solution which is able to remove at least part of the acidicphosphorus compounds. It is possible to use an additional organicnitrogen compound which is capable of reacting with the acidicphosphorus compounds, with the reaction product of nitrogen compound andphosphorus compound likewise being neutralized and removed by treatmentwith the aqueous buffer solution. Methods of stabilizing organophosphiteligands against hydrolytic degradation, of stabilizingmetal-organophosphite catalyst complexes against deactivation and ofreacting one or more reactants in the presence of metal-organophosphitecatalyst complexes, in each of which a treatment with an aqueous buffersolution is carried out, have also been described. U.S. Pat. No.5,741,944 describes an analogous method of separating acidic phosphoruscompounds from hydroformylation product mixtures. U.S. Pat. No.5,874,640 describes an analogous method of removing acidic phosphoruscompounds from reaction product mixtures comprising metal catalystcomplexes with organophosphorus ligands in general. Application of themethod to reaction solutions containing phosphoramidite ligands is notdescribed.

WO 97/20795, U.S. Pat. Nos. 5,741,943 and 5,741,945 describe processeswhich comprise reacting one or more reactants in the presence of ametal-organopolyphosphite catalyst complex and, if desired, freeorganopolyphosphite ligand and another, different sterically hinderedorganophosphorus ligand. The latter has the function of an indicatorligand which indicates depletion of the reaction mixture inpolyorganophosphite ligands and at the same time is supposed to keep therhodium in solution in the case of such a depletion.

WO 97/20797, U.S. Pat. Nos. 5,744,649 and 5,786,517 describe methods ofremoving acidic phosphorus compounds from reaction liquids comprisingmetal-organophosphite catalyst complexes by treatment with water. U.S.Pat. No. 5,886,235 describes an analogous method of treating reactionliquids which comprise metal complexes based on organophosphorus ligandsas catalysts in quite general terms.

WO 97/20798 and U.S. Pat. No. 5,731,472 describe methods of stabilizingmetal-organopolyphosphite catalyst complexes against deactivation, inwhich the catalyzed reaction is carried out in the presence of at leastone free, heterocyclic nitrogen compound selected from among diazoles,triazoles, diazines and triazines.

WO 97/20799, U.S. Pat. Nos. 5,763,671 and 5,789,625 relate to methods ofremoving acidic phosphorus compounds from reaction liquids comprisingmetal-organophosphite catalyst complexes by extraction with water andtreatment of the water with an acid-removing substance. U.S. Pat. No.5,917,095 relates to an analogous method in which metal complexes basedon organophosphorus ligands in general are used as catalysts.

WO 97/20800, U.S. Pat. Nos. 5,763,670 and 5,767,321 relate to processesin which organopolyphosphite catalyst complexes are used in the presenceof a sufficient amount of free organopolyphosphite ligand to prevent orreduce hydrolytic degradation of the ligand and deactivation of thecatalyst.

WO 97/20796, U.S. Pat. Nos. 5,763,677 and 5,763,680 describe methods ofseparating one or more acidic phosphorus compounds from reaction liquidscomprising metal-organophosphite catalyst complexes by extraction withwater and treatment of the water with an ion exchanger and optionally anamine. U.S. Pat. No. 5,892,119 describes an analogous method forreaction liquids which comprise metal complexes based onorganophosphorus ligands in general as catalysts. Treatment of reactionliquids comprising catalysts based on phosphoramidite ligands is notdescribed.

It is an object of the present invention to provide an improved processfor the hydroformylation of compounds containing at least oneethylenically unsaturated double bond. It should use hydroformylationcatalysts which make it possible for relatively long-chain, terminal orinternal olefins or industrial mixtures of olefins having terminal andinternal double bonds, e.g. mixtures of 1-butene and 2-butene, to behydroformylated to give good yields of aldehydes having a higherlinearity (n selectivity). A further requirement which thehydroformylation catalysts have to meet is good stability underhydroformylation conditions and thus a long catalyst operating life,since catalyst or ligand losses have a particularly adverse effect onthe economics of a hydroformylation process.

It has now surprisingly been found that this object is achieved by ahydroformylation process in which a metal complex of a metal oftransition group VIII of the Periodic Table of the Elements with atleast one phosphoramidite compound as ligand dissolved in the reactionmedium is used to catalyze the reaction and in which the solution isbrought into contact with a base.

The invention accordingly provides a process for the hydroformylation ofcompounds containing at least one ethylenically unsaturated double bondby reaction with carbon monoxide and hydrogen in at least one reactionzone in the presence of a catalytically active fluid which comprises adissolved metal complex of a metal of transition group VIII of thePeriodic Table of the Elements with at least one phosphoramiditecompound as ligand, wherein the fluid is brought into contact with abase.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 shows a miniplant for carrying out continuous hydroformylationsconsisting of two autoclaves with lifting stirrer connected in series (1and 2), a pressure separator (3), a flash stripping column (4), and anion exchanger bed (5).

FIG. 2 shows a miniplant for carrying out continuous hydroformylations.This consists of two autoclaves with lifting stirrer connected in series(1 and 2), a pressure separator (3), a heated depressurization vesselfor separating off C₄-hydrocarbons (4), a wiped film evaporator (5), andan ion exchanger bed (6).

For the purposes of the present invention, a “phosphoramidite compound”is a phosphorus-containing compound having at least one phosphorus atomto which one, two or three groups are covalently bound via a nitrogenatom, i.e. to form a P—N bond. Phosphoramidite compounds, in particularthose in which one or more substituted pyrrole groups are bound viatheir nitrogen atom to the phosphorus atom, and the hydroformylationcatalysts based on them are known to have a good stability. Theinventors of the present invention have now found that catalysts basedon phosphoramidite ligands can be additionally stabilized againstdegradation of the ligands or deactivation of the catalysts underhydroformylation conditions by bringing the catalytically active fluidinto contact with a base. This is surprising since these ligands alreadycontain more or less basic nitrogen-containing groups. Advantageously,stabilization of the hydroformylation catalysts based on phosphoramiditeligands by bringing them into contact with a base is successful even inthe absence of synthesis gas. The present invention therefore alsoprovides a hydroformylation process comprising the work-up of the outputfrom the reaction zone and recirculation of the catalytically activefluid, with at least one of these steps being carried out in the absenceof carbon monoxide and hydrogen.

For the purposes of the present invention, “bringing into contact”refers both to formation of a single-phase mixture and to contacting viaa phase interface, e.g. liquid/liquid or liquid/solid. The contactingcan be carried out over the total duration of the hydroformylation(including the work-up and recirculation of the catalytically activefluid), part thereof or periodically.

The catalytically active fluid comprises at least one dissolved metalcomplex of a metal of transition group VIII of the Periodic Table of theElements with at least one phosphoramidite compound as ligand. The metalcomplex is thus generally present as a homogeneous single-phase solutionin a suitable solvent. This solution can further comprisephosphoramidite compounds as free ligands. As solvents, preference isgiven to using the relatively high-boiling subsequent reaction productsformed in the hydroformylation of the respective ethylenicallyunsaturated compounds, e.g. the products of aldol condensation.Furthermore, the hydroformylation products can also function as solventsuntil they are separated off.

Aromatics such as toluene and xylenes, hydrocarbons or mixtures ofhydrocarbons are likewise suitable as solvents. Further suitablesolvents are esters of aliphatic carboxylic acids with alkanols, forexample ethyl acetate or Texanol®, ethers such as tert-butyl methylether and tetrahydrofuran. In the case of sufficiently hydrophilicligands, it is also possible to use alcohols such as methanol, ethanol,n-propanol, isopropanol, n-butanol, isobutanol, ketones such as acetoneand methyl ethyl ketone, etc. Furthermore, “ionic liquids” can also beused as solvents. These are liquid salts, for exampleN,N′-dialkylimidazolium salts such as N-butyl-N′-methylimidazoliumsalts, tetraalkylammonium salts such as tetra-n-butylammonium salts,N-alkylpyridinium salts such as n-butylpyridinium salts,tetraalkylphosphonium salts such as trishexyl(tetradecyl)phosphoniumsalts, e.g. the tetrafluoroborates, acetates, tetrachloroaluminates,hexafluorophosphates, chlorides and tosylates.

The hydroformylation is carried out in at least one reaction zone whichcan comprise one or more, identical or different reactors. In thesimplest case, the reaction zone is formed by a single reactor. Both thereactors of each individual zone and the reactors which may formdifferent stages can in each case have identical or different mixingcharacteristics. The reactors can, if desired, be divided one or moretimes by means of internals. If two or more reactors form one zone,these can be connected in any desired way, e.g. in parallel or inseries.

Suitable pressure-rated reaction apparatuses for the hydroformylationare known to those skilled in the art. They include the generallycustomary reactors for gas-liquid reactions, e.g. tube reactors, stirredvessels, gas circulation reactors, bubble columns, etc., which may, ifappropriate, be divided by internals.

Carbon monoxide and hydrogen are usually used in the form of a mixtureknown as synthesis gas. The composition of the synthesis gas used in theprocess of the invention can vary within a wide range. The molar ratioof carbon monoxide to hydrogen is generally from 1:1000 to 1000:1,preferably from 1:100 to 100:1. If a plurality of reaction zones areused, these can have identical or different molar ratios of CO to H₂.

The temperature in the hydroformylation reaction is generally in therange from about 20 to 200° C., preferably from about 50 to 190° C., inparticular from about 60 to 150° C. The reaction is preferably carriedout at a pressure in the range from about 1 to 700 bar, particularlypreferably from 3 to 600 bar, in particular from 5 to 50 bar. Thereaction pressure can be varied as a function of the activity of thehydroformylation catalyst used. Thus, the hydroformylation catalystsdescribed in more detail below sometimes allow a reaction in a lowerpressure range, for instance in the range from about 1 to 100 bar. If aplurality of reaction zones are used, these can be operated at identicalor different temperatures and/or pressures.

The hydroformylation can be carried out batchwise or continuously.Preference is given to a continuous process wherein

-   a) the ethylenically unsaturated compound(s) and carbon monoxide and    hydrogen are fed into the reaction zone(s) and are reacted in the    presence of the catalytically active fluid,-   b) an output is taken from the reaction zone and is subjected to a    fractionation to give a fraction consisting essentially of the    hydroformylation product and a fraction comprising the catalytically    active fluid in which the by-products of the hydroformylation which    have boiling points higher than that of the hydroformylation product    are present and the metal complex is dissolved, and-   c) the catalytically active fluid is, if appropriate after    separating off at least part of the by-products having boiling    points higher than that of the hydroformylation product,    recirculated to the reaction zone.

The output from the reaction zone is subjected to a single-stage ormultistage separation operation to give a stream comprising the majorpart of the hydroformylation product and a stream comprising thecatalytically active fluid. Depending on the discharge and separationmethods employed, further streams are generally obtained, e.g. offgasescomprising synthesis gas, streams comprising unreacted ethylenicallyunsaturated compound with or without saturated hydrocarbon etc. Thesecan be recirculated partly or in their entirety to the reaction zone orbe discharged from the process.

Preference is given to taking a liquid output from the reaction zone(liquid discharge process). This liquid output comprises, as significantconstituents:

-   i) the hydroformylation product, i.e. the aldehydes produced from    the olefin or olefin mixture used,-   ii) the high-boiling by-products of the hydroformylation, as result    from, for example, the aldol reaction of the aldehydes formed,-   iii) the homogeneously dissolved hydroformylation catalyst and    possibly free ligand,-   iv) possibly unreacted olefins,-   v) low-boiling components such as alkanes, and-   vi) dissolved synthesis gas.

If an inert solvent is used for the hydroformylation, this is alsopresent in the liquid output from the reaction zone. However, theby-products which are formed in the hydroformylation (e.g. by aldolcondensation) and have boiling points higher than that of thehydroformylation product are generally used as solvent.

The fractionation of the liquid output from the reaction zone to givefirstly a fraction consisting essentially of the hydroformylationproduct and, secondly, the catalytically active fluid in which theby-products of the hydroformylation which have boiling points higherthan that of the hydroformylation product are present and the metalcomplex is dissolved is carried out by conventional methods known tothose skilled in the art. These include depressurization and thermalfractionation steps (distillations). Suitable separation apparatuses fora distillation are, for example, distillation columns such as traycolumns which may, if desired, be equipped with bubble caps, sieveplates, sieve trays, valves, etc., evaporators such as thin filmevaporators, falling film evaporators, wiped film evaporators, etc.

The liquid output from the reaction zone can, for example, be worked upby firstly subjecting it to a single-stage or multistage degassingoperation.

In one embodiment with single-stage degassing, the liquid output fromthe reaction zone is, for example, depressurized into a depressurizationvessel and, as a result of the reduction in pressure, the output isseparated into a liquid phase comprising the hydroformylation catalystand, if present, free ligands, the high-boiling by-products of thehydroformylation and a gaseous phase comprising the major part of thehydroformylation product formed, any unreacted olefins, low-boilingcomponents and excess synthesis gas. The liquid phase forming thecatalytically active fluid can, in order to recycle the catalyst, bereturned as a recycle stream, if appropriate after separating off atleast part of the high-boiling by-products, to the reaction zone. Thegas phase can be worked up further by passing it to, for example, acondenser in which the hydroformylation product is separated off inliquid form. The gas phase obtained in the condenser, which consistsessentially of unreacted synthesis gas, unreacted olefin and inertcomponents, can, if appropriate after separating off at least part ofthe inert components, be returned either wholly or partly to thereaction zone.

In a further embodiment of the liquid discharge process with degassing,the liquid output from the reaction zone is worked up by subjecting to atwo-stage degassing operation. Here, the first degassing stage can alsobe configured as a calming zone in which no gas is introduced into theliquid phase. The gas phase obtained in this calming/depressurizationstage consists essentially of synthesis gas. The liquid phase obtainedfrom the calming/depressurization stage can in turn be separated into aliquid phase and a gas phase in a second depressurization stage(degassing stage). The second liquid phase obtained in this waygenerally comprises the by-products having boiling points higher thanthat of the hydroformylation product, the homogeneously dissolved firsthydroformylation catalyst and possibly part of the hydroformylationproduct. The second gas phase comprises the unreacted olefin, saturatedhydrocarbons and likewise part of the hydroformylation product. Toisolate firstly the catalytically active fluid and secondly a fractioncomprising the major part of the hydroformylation product, the seconddepressurization stage can be followed by a thermal work-up. Thisthermal separation step can be, for example, a distillation. In thedistillation, the second liquid phase and the second gas phase from thesecond depressurization step are preferably conveyed in countercurrentand thus brought into particularly intimate contact (stripping). In apreferred embodiment, the second depressurization stage is configured asa combination of the depressurization step (flash) with a thermalseparation step (flash/stripping stage).

As an alternative to the above-described pure liquid dischargeprocesses, it is also possible to use the gas recycle process in which afurther gaseous output is taken from the gas space of the reaction zone.This gaseous output consists essentially of synthesis gas, unreactedolefins and inert components, and, depending on the vapor pressure ofthe hydroformylation product in the reaction zone, part of thehydroformylation products formed may also be discharged in this gaseousoutput. The hydroformylation product carried out with the gas stream canbe condensed out by, for example, cooling and the gas stream which hasbeen freed of the liquid fraction can be returned to the reaction zone.

The bases used in the process of the invention are preferably selectedfrom among bases soluble in the catalytically active fluid, basesimmobilized on a solid phase and combinations thereof. The base ispreferably selected from among basic nitrogen compounds.

Particularly preferred bases are nitrogen compounds which have noprimary and secondary nitrogen atoms (i.e. ones to which H atoms arestill bound). Basic nitrogen compounds which contain compounds havingprimary and secondary nitrogen atoms as impurities, e.g. tertiary amineswhich are, as a result of the method by which they are produced,contaminated with primary and/or secondary amines, can be subjected to awork-up to remove at least part of these compounds before they are usedin the process of the invention.

Suitable bases are, for example, trialkylamines. Trialkylamines whichhave a boiling point below or in the region of that of the productaldehydes, as is generally the case for tri(C₁-C₃-)alkylamines, are lesssuitable if the product aldehydes are separated from the reactionproduct mixture by distillation.

Preference is also given to the base being selected from amongdialkylarylamines, preferably di(C₁-C₄-)alkylarylamines, where the alkylgroups and/or the aryl group may be substituted further. The aryl groupis preferably phenyl. Such compounds include, for example,N,N-dimethylaniline, N,N-diethylaniline, N,N,2,4,6-pentamethylaniline,bis(4-(N,N-dimethylamino)phenyl)methylene,4,4′-bis(N,N-dimethylamino)benzo-phenone, etc.

Preference is also given to the base being selected from amongalkyldiarylamines, preferably (C₁-C₄-)alkyldiarylamines, where the alkylgroup and/or the aryl group may be substituted. Such compounds include,for example, diphenylmethylamine and diphenylethylamine.

Preference is also given to the base being selected from amongtriarylamines, where the aryl groups may be substituted, for exampletriphenylamine, etc. Further preferred amines are tricycloalkylamines,such as tricyclohexylamine.

Preference is also given to the base being selected from amongnitrogen-containing heterocycles. The nitrogen-containing heterocyclesare preferably selected from the group consisting of pyrroles,pyrrolidines, pyridines, quinolines, isoquinolines, purines, pyrazoles,imidazoles, triazoles, tetrazoles, indolizines, pyridazines,pyrimidines, pyrazines, triazines, indoles, isoindoles, oxazoles,oxazolidones, oxazolidines, morpholines, piperazines, piperidines andderivatives thereof.

Suitable derivatives of the abovementioned nitrogen-containingheterocycles can have, for example, one or more C₁-C₆-alkyl substituentssuch as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, etc.

Heterocycles preferred as bases are pyrroles, indoles, pyridines,quinolines and triazoles, which may additionally bear one or moreC₁-C₆-alkyl substituents. Such compounds include, for example,3-alkylindoles, such as 3-methylindole, 2,6-dialkylpyridines, such as2,6-dimethylpyridine, quinoline and 1-H-benzotriazole.

The abovementioned bases can be used either individually or in the formof any mixtures.

When at least one base which is soluble in the catalytically activefluid is used, a molar ratio of base to phosphoramidite compound of from0.01:1 to 5:1, preferably from 0.1:1 to 1.5:1, is preferably maintainedin the reaction zone. For this purpose, for example, the pH of thereaction mixture can be monitored at regular intervals and base can beadded to the reaction mixture if necessary.

If the work-up of the reaction output encompasses, as described above, athermal separation step, preference is given to using high-boilingsoluble bases which have a boiling point under the conditions of thethermal work-up which is sufficiently above those of thehydroformylation products. The output from the reaction zone ispreferably fractionated so that the resulting fraction comprising thehydroformylation product is essentially free of the base used. Thefractionation of the output from the reaction zone is preferably alsocarried out so that essentially all the base is present in the fractionforming the catalytically active fluid and is recirculated to thereaction zone together with this.

In one embodiment of the process of the invention, at least one baseimmobilized on a solid phase is used as base. Suitable immobilized basesare in principle the basic ion exchangers known to those skilled in theart. The solid phase of these basic ion exchangers comprises, forexample, a polymer matrix. Such matrices include, for example,polystyrene matrices which comprise copolymers of styrene and at leastone crosslinking monomer, e.g. divinylbenzene, together with, ifappropriate, further comonomers. Further suitable matrices arepolyacrylic matrices obtained by polymerization of at least one(meth)acrylate, at least one crosslinking monomer and, if appropriate,further comonomers. Suitable polymer matrices also includephenol-formaldehyde resins and polyalkylamine resins which are obtained,for example, by condensation of polyamines with epichlorohydrin.

The anchor groups which are bound to the solid phase either directly orvia a spacer group (and whose loosely bound counterions can be replacedby ions bearing a charge of the same sign) are preferably selected fromamong nitrogen-containing groups, preferably tertiary and quaternaryamino groups. Preference is given to anchor groups which are present inthe free base form.

Examples of suitable functional groups are (in order of decreasingbasicity):

-   -   —CH₂N⁺(CH₃)₃OH⁻e.g. Duolite A 101    -   —CH₂N⁺(CH₃)₂CH₂CH₂OH OH⁻e.g. Duolite A 102    -   —CH₂N(CH₃)₂ e.g. Amberlite IRA 67    -   —CH₂NHCH₃    -   —CH₂NH₂ e.g. Duolite A 365

Both strongly basic and weakly basic ion exchangers are suitable for theprocess of the invention, with preference being given to weakly basicion exchangers. Among weakly basic ion exchangers, preference is givento those containing tertiary amino groups. Strongly basic ion exchangersgenerally have quaternary ammonium groups as anchor groups. A weaklybasic ion exchanger is generally present in the free base form afterregeneration.

Commercially available ion exchangers suitable for the process of theinvention are, for example, Amberlite® IRA 67 and Amberlyst A21.

Ion exchangers usually have a hydrophilic sphere of bound water. Thebases immobilized on a solid phase are preferably brought into contactwith at least one anhydrous solvent to remove part or all of the boundwater before they are used in the process of the invention. In such acase, preference is given to firstly treating the ion exchanger with awater-soluble or water-miscible solvent and subsequently with anessentially water-insoluble solvent. Suitable water-miscible solventsare, for example, alcohols such as methanol, ethanol, n-propanol,isopropanol etc. Suitable essentially water-insoluble solvents are, forexample, aromatics such as toluene and xylenes, hydrocarbons andhydrocarbon mixtures and also high-boiling alcohols, e.g.2-propylheptanol. It has surprisingly been found that the ion exchangersused according to the invention are also suitable for stabilizingphosphoramidite compounds against degradation or protecting thecorresponding hydroformylation catalysts from deactivation in anessentially water-free medium.

The catalytically active fluid is preferably brought into contact withan immobilized base by taking a liquid output from the reaction zone andbringing it into contact with the immobilized base before or after it isfractionated. Preference is given to the fraction forming thecatalytically active fluid which is obtained by fractionation of theoutput being brought into contact with the immobilized base. The basecan be present either in the form of a slurry or in the form of packing,e.g. as a fixed bed.

The regeneration of the immobilized base is carried out by conventionalmethods known to those skilled in the art, e.g. treatment with aqueousbase. Suitable bases are, for example, ammonium, alkali metal carbonatessuch as sodium carbonate and potassium carbonate, and alkali metalhydroxides such as sodium hydroxide and potassium hydroxide. Preferenceis given to firstly carrying out the treatment with one of theabovementioned water-soluble or water-miscible solvents beforeregeneration. Regeneration is preferably followed by at least onerinsing step using a dry organic solvent, as described above. Here too,particular preference is given to firstly carrying out a treatment witha water-soluble or water-miscible solvent and subsequently with anessentially water-insoluble solvent.

In a preferred embodiment of the process of the invention, a combinationof at least one base soluble in the catalytic fluid and at least onebase immobilized on a solid phase is used. The base pairs are selectedso that the immobilized bases are capable of at least partly liberatingthe soluble bases from the acid-base adducts obtained by reaction of thesoluble bases with acids. For this purpose, the bases are selected sothat the base strengths of the liquid bases under the reactionconditions are lower than the base strengths of the immobilized bases.These base strengths can readily be determined by a person skilled inthe art by means of simple routine experiments. A good guide is providedby the pK_(b) values for the bases which are generally known for use inaqueous systems.

Phosphoramidite compounds suitable for use in the process of theinvention are described in WO 00/56451, WO 02/083695, WO 03/018192 andthe German patent application 102 43 138.8, which are hereby fullyincorporated by reference.

The metal of transition group VIII of the Periodic Table is preferablyCo, Ru, Rh, Pd, Pt, Os or Ir, especially Rh, Co, Ir or Ru.

In the following, the expression “alkyl” encompasses straight-chain andbranched alkyl groups. The alkyl groups are preferably straight-chain orbranched C₁-C₂₀-alkyl groups, more preferably C₁-C₁₂-alkyl groups,particularly preferably C₁-C₈-alkyl groups and very particularlypreferably C₁-C₄-alkyl groups. Examples of alkyl groups are, inparticular, methyl, ethyl, propyl, isopropyl, n-butyl, 2-butyl,sec-butyl, tert-butyl, n-pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl,1,2-dimethylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl,1-ethylpropyl, n-hexyl, 2-hexyl, 2-methylpentyl, 3-methylpentyl,4-methylpentyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl,1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl,1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethylbutyl,2-ethylbutyl, 1-ethyl-2-methylpropyl, n-heptyl, 2-heptyl, 3-heptyl,2-ethylpentyl, 1-propylbutyl, n-octyl, 2-ethylhexyl, 2-propylheptyl,nonyl, decyl.

The expression “alkyl” also encompasses substituted alkyl groups whichcan generally bear 1, 2, 3, 4 or 5 substituents, preferably 1, 2 or 3substituents and particularly preferably 1 substituent, selected fromamong the groups cycloalkyl, aryl, hetaryl, halogen, NE¹E², NE¹E²E³⁺,COOH, carboxylate, —SO₃H and sulfonate, where E¹, E² and E³ areidentical or different radicals selected from among hydrogen, alkyl,cycloalkyl and aryl.

For the purposes of the present invention, the expression “alkylene”refers to straight-chain or branched alkanediyl groups having from 1 to4 carbon atoms.

For the purposes of the present invention, the expression “cycloalkyl”encompasses both unsubstituted and substituted cycloalkyl groups,preferably C₅-C₇-cycloalkyl groups, such as cyclopentyl, cyclohexyl orcycloheptyl, which, if they are substituted, can generally bear 1, 2, 3,4 or 5 substituents, preferably 1, 2 or 3 substituents and particularlypreferably 1 substituent, selected from among the groups alkyl, alkoxyand halogen.

For the purposes of the present invention, the expression“heterocycloalkyl” encompasses saturated, cycloaliphatic groups whichgenerally have from 4 to 7, preferably 5 or 6, ring atoms and in which 1or 2 of the ring carbons are replaced by heteroatoms selected from amongthe elements oxygen, nitrogen and sulfur and which may be substituted.If they are substituted, these heterocycloaliphatic groups can bear 1, 2or 3 substituents, preferably 1 or 2 substituents, particularlypreferably 1 substituent, selected from among alkyl, aryl, COOR^(f)(R^(f)=hydrogen, alkyl, cycloalkyl or aryl), COO⁻M⁺and NE¹E², preferablyalkyl. Examples of such heterocycloaliphatic groups are pyrrolidinyl,piperidinyl, 2,2,6,6-tetramethylpiperidinyl, imidazolidinyl,pyrazolidinyl, oxazolidinyl, morpholidinyl, thiazolidinyl,isothiazolidinyl, isoxazolidinyl, piperazinyl, tetrahydrothiophenyl,tetrahydrofuranyl, tetrahydropyranyl, dioxanyl.

For the purposes of the present invention, the expression “aryl”encompasses both unsubstituted and substituted aryl groups andpreferably refers to phenyl, tolyl, xylyl, mesityl, naphthyl, fluorenyl,anthracenyl, phenanthrenyl or naphthacenyl, particularly preferablyphenyl or naphthyl. If they are substituted, these aryl groups cangenerally bear 1, 2, 3, 4 or 5 substituents, preferably 1, 2 or 3substituents and particularly preferably 1 substituent, selected fromamong the groups alkyl, alkoxy, carboxyl, carboxylate, trifluoromethyl,—SO₃H, sulfonate, NE¹E², alkylene-NE¹E², nitro, cyano and halogen.

For the purposes of the present invention, the expression “hetaryl”refers to unsubstituted or substituted, heterocycloaromatic groups,preferably the groups pyridyl, quinolinyl, acridinyl, pyridazinyl,pyrimidinyl, pyrazinyl, and also the subgroup of “pyrrole groups”. Ifthey are substituted, these heterocycloaromatic groups can generallybear 1, 2 or 3 substituents selected from among the groups alkyl,alkoxy, carboxyl, carboxylate, —SO₃H, sulfonate, NE¹E², alkylene-NE¹E²,trifluoromethyl or halogen.

For the purposes of the present invention, the expression “pyrrolegroup” refers to a series of unsubstituted or substituted,heterocycloaromatic groups which are derived structurally from thepyrrole skeleton and have a pyrrolic nitrogen atom in the heterocyclewhich can be linked covalently to other atoms, for example a pnicogenatom. The expression “pyrrole group” thus encompasses the unsubstitutedor substituted groups pyrrolyl, imidazolyl, pyrazolyl, indolyl, purinyl,indazolyl, benzotriazolyl, 1,2,3-triazolyl, 1,3,4-triazolyl andcarbazolyl, which, if they are substituted, can generally bear 1, 2 or 3substituents, preferably 1 or 2 substituents, particularly preferably 1substituent, selected from among the groups alkyl, alkoxy, acyl,carboxyl, carboxylate, —SO₃H, sulfonate, NE¹E², alkylene-NE¹E²,trifluoromethyl and halogen. A preferred substituted indolyl group isthe 3-methylindolyl group.

Accordingly, the expression “bispyrrole group” encompasses, for thepurposes of the present invention, divalent groups of the formulaPy-I-Py,which contain two pyrrole groups bound via a direct chemical bond or alink comprising alkylene, oxa, thio, imino, silyl or alkylimino groups,for example the bisindole diyl group of the formula

as an example of a bispyrrole group containing two directly linkedpyrrole groups, in this case indolyl, or the bispyrrole diylmethanegroup of the formula

as an example of a bispyrrole group containing two pyrrole groups, inthis case pyrrolyl, linked via a methylene group. Like the pyrrolegroups, the bispyrrole groups can also be unsubstituted or substitutedand, if they are substituted, generally bear 1, 2 or 3 substitutents,preferably 1 or 2 substituents, in particular 1 substituent, selectedfrom among alkyl, alkoxy, carboxyl, carboxylate, —SO₃H, sulfonate,NE¹E², alkylene-NE¹E², trifluoromethyl and halogen per pyrrole groupunit. In these indications of the number of possible substituents, thelink between the pyrrole group units via a direct chemical bond or viathe link comprising the abovementioned groups is not regarded assubstitution.

For the purposes of the present invention, carboxylate and sulfonate arepreferably derivatives of a carboxylic acid function or a sulfonic acidfunction, in particular a metal carboxylate or sulfonate, a carboxylicester or sulfonic ester function or a carboxamide or sulfonamidefunction. Such functions include, for example, the esters withC₁-C₄-alkanols, such as methanol, ethanol, n-propanol, isopropanol,n-butanol, sec-butanol and tert-butanol, and also primary amides andtheir N-alkyl and N,N-dialkyl derivatives.

What has been said above with regard to the expressions “alkyl”,“cycloalkyl”, “aryl”, “heterocycloalkyl” and “hetaryl” appliesanalogously to the expressions “alkoxy”, “cycloalkoxy”, “aryloxy”,“heterocycloalkoxy” and “hetaryloxy”.

For the purposes of the present invention, the expression “acyl” refersto alkanoyl or aroyl groups which generally have from 2 to 11,preferably from 2 to 8 carbon atoms, for example the acetyl, propanoyl,butanoyl, pentanoyl, hexanoyl, heptanoyl, 2-ethylhexanoyl,2-propylheptanoyl, benzoyl or naphthoyl group.

The radicals E¹ to E¹² are selected independently from among hydrogen,alkyl, cycloalkyl and aryl. The groups NE¹E², NE⁴E⁵, NE⁷E⁸ and NE¹⁰E¹¹are preferably N,N-dimethylamino, N,N-diethylamino, N,N-dipropylamino,N,N-diisopropylamino, N,N-di-n-butylamino, N,N-di-t-butylamino,N,N-dicyclohexylamino or N,N-diphenylamino.

Halogen is fluorine, chlorine, bromine or iodine, preferably fluorine,chlorine or bromine.

M⁺is a cation equivalent, i.e. a monovalent cation or the part of apolyvalent cation corresponding to a single positive charge. The cationM⁺serves merely as counterion to neutralize negatively chargedsubstituent groups such as the COO^(—)or sulfonate group and can inprinciple be selected freely. Preference is therefore given to usingalkali metal ions, in particular Na⁺, K⁺, Li⁺ions, or onium ions such asammonium, monoalkylammonium, dialkylammonium, trialkylammonium,tetraalkylammonium, phosphonium, tetraalkylphosphonium ortetraarylphosphonium ions.

An analogous situation applies to the anion equivalent X⁻, which servesmerely as counterion of positively charged substituent groups such asammonium groups and can be selected freely from among monovalent anionsand the parts of a polyvalent anion corresponding to a single negativecharge. Suitable anions are, for example, halide ions X⁻, such aschloride and bromide. Preferred anions are sulfate and sulfonate, e.g.SO₄ ²⁻, tosylate, trifluoromethanesulfonate and methylsulfonate.

x and y are each an integer from 1 to 240, preferably an integer from 3to 120.

Fused ring systems can be aromatic, hydroaromatic and cyclic compoundsjoined by fusion. Fused ring systems comprise two, three or more rings.Depending on the way the rings are linked, a distinction is made in thecase of fused ring systems between ortho-fusion, i.e. each ring sharesan edge or two atoms with each adjacent ring, and peri-fusion in whichone carbon atom belongs to more than two rings. Among fused ringsystems, preference is given to ortho-fused ring systems.

The phosphoramidite compound used in the process of the invention ispreferably selected from among compounds of the formulae I and II

where

-   R¹ and R⁵ are each, independently of one another, pyrrole groups    bound via the nitrogen atom to the phosphorus atom,-   R², R³ and R⁴ are each, independently of one another, alkyl,    cycloalkyl, heterocycloalkyl, aryl or hetaryl,    -   or R¹ together with R² and/or R⁴ together with R⁵ forms a        divalent group containing at least one pyrrole group bound via        the pyrrolic nitrogen atom to the phosphorus atom,-   Y is a divalent bridging group having from 2 to 20 bridge atoms    between the flanking bonds,-   X¹, X², X³ and X⁴ are selected independently from among O, S,    SiR^(α)R^(β)and NR^(γ), where R^(α), R^(β)and R^(γ)are each,    independently of one another, hydrogen, alkyl, cycloalkyl,    heterocycloalkyl, aryl or hetaryl, and-   a, b, c and d are each, independently of one another, 0 or 1.

The radicals R², R³ and R⁴ in the formulae (I) and (II) can be,independently of one another, alkyl, cycloalkyl, heterocycloalkyl, arylor hetaryl, where the alkyl radicals may have 1, 2, 3, 4 or 5substituents selected from among cycloalkyl, heterocycloalkyl, aryl,hetaryl, alkoxy, cycloalkoxy, heterocycloalkoxy, aryloxy, hetaryloxy,hydroxy, thiol, polyalkylene oxide, polyalkylenimine, COOH, carboxylate,SO₃H, sulfonate, NE⁷E⁸, NE⁷E⁸E⁹⁺X⁻, halogen, nitro, acyl and cyano,where E⁷, E⁸ and E⁹ are identical or different radicals selected fromamong hydrogen, alkyl, cycloalkyl and aryl and X⁻is an anion equivalent,and the cycloalkyl, heterocycloalkyl, aryl and hetaryl radicals R², R³and R⁴ may each have 1, 2, 3, 4 or 5 substituents selected from amongalkyl and the substituents mentioned above for the alkyl radicals R², R³and R⁴.

The substituents R², R³ and/or R⁴ are advantageously also pyrrole groupsbound via the pyrrolic nitrogen atom to the phosphorus atom.

The phosphoramidite compounds used in the process of the invention areparticularly preferably selected from among chelating phosphoramidites.Particularly preferred chelating phosphoramidites are thephosphoramidite compounds of the formula II.1

where

-   R¹, R², R⁴, R⁵, Y, b and c are as defined above.

In a first preferred embodiment, the substituents R¹, R², R⁴ and R⁵ arepyrrole groups bound via the pyrrolic nitrogen atom to the phosphorusatom, with R¹ not being bound to R² and R⁴ not being bound to R⁵. Themeaning of the term pyrrole group here corresponds to the definitiongiven above.

Preference is given to chelating phosphorus compounds in which theradicals R¹, R², R⁴ and R⁵ are selected independently from among groupsof the formulae III.a to III.k

where

-   alk is a C₁-C₁₂-alkyl group and-   R^(a), R^(b), R^(c) and R^(d) are each, independently of one    another, hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, acyl, halogen,    C₁-C₄-alkoxycarbonyl or carboxyl.

For the purposes of illustration, some advantageous pyrrole groups arelisted below:

A particularly advantageous group is the 3-methylindolyl group (skatolylgroup) of the formula III.f1. Hydroformylation catalysts based onligands having one or more 3-methylindolyl group(s) bound to thephosphorus atom have a particularly high stability and thus particularlylong catalyst operating lives even without stabilization by a base.

In a further advantageous embodiment of the present invention, thesubstituent R¹ together with the substituent R² and/or the substituentR⁴ together with the substituent R⁵ in the formulae I, II and II.1 canform a divalent group comprising a pyrrole group bound via the pyrrolicnitrogen atom to the phosphorus atom and having the formulaPy-I—W,where

-   Py is a pyrrole group,-   I is a chemical bond or O, S, SiR^(π)R^(χ),NR^(ω)or optionally    substituted C₁-C₁₀-alkylene, preferably CR^(λ)R^(μ),-   W is cycloalkyloxy or cycloalkylamino, aryloxy or arylamino,    hetaryloxy or hetarylamino    and-   R^(π), R^(χ), R^(ω), R^(λ)and R^(μ)are each, independently of one    another, hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or    hetaryl,    where the terms used here have the meanings indicated above.

Preferred divalent groups of the formulaPy-I—Ware, for example:

Preference is given to phosphoramidites in which the substituent R¹together with the substituent R² and/or the substituent R⁴ together withthe substituent R⁵ forms a bispyrrole group of the formula

where

-   I is a chemical bond or O, S, SiR^(π)R^(χ), NR^(ω)or optionally    substituted C₁-C₁₀-alkylene, preferably CR^(λ)R^(μ), where R^(π),    R^(χ), R^(ω), R^(λ)and R^(μ)are each, independently of one another,    hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl,-   R¹⁵, R^(15′), R¹⁶, R^(16′), R¹⁷, R^(17′), R¹⁸ and R^(18′)are each,    independently of one another, hydrogen, alkyl, cycloalkyl,    heterocycloalkyl, aryl, hetaryl, W′COOR^(f), W′COO⁻M⁺, W′(SO₃)R^(f),    W′(SO₃)⁻M⁺, W′PO₃(R^(f))(R^(g)), W′(PO₃)²⁻(M⁺)₂, W′NE¹⁰E¹¹,    W′(NE¹⁰E¹¹E¹²)⁺X⁻, W′OR^(f), W′SR^(f), (CHR^(g)CH₂O)_(x)R^(f),    (CH₂NE¹⁰)_(x) R^(f), (CH₂CH₂NE¹⁰)_(x)R^(f), halogen,    trifluoromethyl, nitro, acyl or cyano,    -   where    -   W′ is a single bond, a heteroatom, a heteroatom-containing group        or a divalent bridging group having from 1 to 20 bridge atoms,    -   R^(f), E¹⁰, E¹¹, E¹² are identical or different radicals        selected from among hydrogen, alkyl, cycloalkyl and aryl,    -   R^(g) is hydrogen, methyl or ethyl,    -   M⁺is a cation equivalent,    -   X⁻is an anion equivalent and    -   x is an integer from 1 to 240,        where two adjacent radicals R¹⁵ and R¹⁶ and/or R^(15′)and        R^(16′)together with the carbon atoms of the pyrrole ring to        which they are bound may also form a fused ring system having 1,        2 or 3 further rings.

I is preferably a chemical bond or a C₁-C₄-alkylene group, particularlypreferably a methylene group.

For the purposes of illustration, a few advantageous “bispyrrolylgroups” are listed below:

In a preferred embodiment, the bridging group Y in the formulae (I),(II) and (II.1) is selected from among groups of the formulae IV.a toIV.u

where

-   R^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV), R^(IV′),    R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), R^(XI) and R^(XII)    are each, independently of one another, hydrogen, alkyl, cycloalkyl,    heterocycloalkyl, aryl, hetaryl, hydroxy, thiol, polyalkylene oxide,    polyalkylenimine, alkoxy, halogen, SO₃H, sulfonate, NE¹E²,    alkylene-NE¹E², nitro, alkoxycarbonyl, carboxyl, acyl or cyano,    where E¹ and E² are identical or different radicals selected from    among hydrogen, alkyl, cycloalkyl and aryl,-   Z is O, S, NR^(δ)or SiR^(δ)R^(ε), where R^(δ)and R^(ε)are each,    independently of one another, hydrogen, alkyl, cycloalkyl,    heterocycloalkyl, aryl or hetaryl,    -   or Z is a C₁-C₄-alkylene bridge which may have a double bond        and/or bear an alkyl, cycloalkyl, heterocycloalkyl, aryl or        hetaryl substituent,    -   or Z is a C₂-C₄-alkylene bridge which is interrupted by O, S or        NR^(δ)or SiR^(δ)R^(ε),        where, in the groups of the formulae IV.a and IV.b, two adjacent        radicals R^(I) to R^(VI) together with the carbon atoms of the        benzene ring to which they are bound may also form a fused ring        system having 1, 2 or 3 further rings,        where, in the groups of the formulae IV.h to IV.n, two geminal        radicals R^(I), R^(I′); R^(II), R^(II′); R^(III), R^(III′)and/or        R^(IV), R^(IV′)may also represent oxo or a ketal thereof,        A¹ and A² are each, independently of one another, O, S,        SiR^(φ)R^(γ), NR^(η)or CR^(ι)R^(κ), where R^(φ), R^(γ), R^(η),        R^(ι)and R^(κ)are each, independently of one another, hydrogen,        alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl,-   A³ and A⁴ are each, independently of one another, SiR^(φ), N or    CR^(ι),-   D is a divalent bridging group of the formula

-   -   where

-   R⁹, R^(9′), R¹⁰ and R^(10′)are each, independently of one another,    hydrogen, alkyl, cycloalkyl, aryl, halogen, trifluoromethyl,    carboxyl, carboxylate or cyano,    where R^(9′)together with R^(10′)can also represent the second bond    of a double bond between the two carbon atoms to which R^(9′)and    R^(10′)are bound, and/or R⁹ and R¹⁰ together with the carbon atoms    to which they are bound may also form a 4- to 8-membered carbocycle    or heterocycle which may additionally be fused with one, two or    three cycloalkyl, heterocycloalkyl, aryl or hetaryl groups, where    the heterocycle and, if present, the fused-on groups may each bear,    independently of one another, one, two, three or four substituents    selected from among alkyl, cycloalkyl, heterocycloalkyl, aryl,    hetaryl, COOR^(f), COO⁻M⁺, SO₃R^(f), SO⁻ ₃M⁺, NE⁴E⁵, alkylene-NE⁴E⁵,    NE⁴E⁵E⁶⁺X⁻, alkylene-NE⁴E⁵E⁶⁺X⁻, OR^(f), SR^(f),    (CHR^(e)CH₂O)_(y)R^(f), (CH₂N(E⁴))_(y)R^(f), (CH₂CH₂N(E⁴))_(y)R^(f),    halogen, trifluoromethyl, nitro, acyl and cyano, where

-   R^(f), E⁴, E⁵ and E⁶ are identical or different radicals selected    from among hydrogen, alkyl, cycloalkyl and aryl,

-   R^(e) is hydrogen, methyl or ethyl,

-   M⁺is a cation,

-   X⁻is an anion and

-   y is an integer from 1 to 240.

Preference is given to the bridging group Y being a group of the formulaIV.a in which the groups A¹ and A² are selected from among the groups O,S and CR^(i)R^(k), in particular from among O, S, the methylene group(R^(i)=R^(k)=H), the dimethylmethylene group (R^(i)=R^(k)=CH₃), thediethylmethylene group (R^(i)=R^(k)=C₂H₅), the di-n-propylmethylenegroup (R^(i)=R^(k)=n-propyl) or the di-n-butylmethylene group(R^(d)=R^(e)=n-butyl). Particular preference is given to bridging groupsY in which A¹ is different from A², with A¹ preferably being aCR^(i)R^(k) group and A² preferably being an O or S group, particularlypreferably an oxa group O.

Preference is given to the bridging group Y being a group of the formulaIV.b in which D is a divalent bridging group selected from among thegroups

where R⁹, R^(9′), R¹⁰ and R^(10′)are each, independently of one another,hydrogen, alkyl, cycloalkyl, aryl, halogen, trifluoromethyl, carboxyl,carboxylate or cyano or are joined to one another to form aC₃-C₄-alkylene group and R¹¹, R¹², R¹³ and R¹⁴ can each be,independently of one another, hydrogen, alkyl, cycloalkyl, aryl,halogen, trifluoromethyl, COOH, carboxylate, cyano, alkoxy, SO₃H,sulfonate, NE¹E², alkylene-NE¹E²E³⁺X⁻, aryl or nitro. Preference isgiven to the groups R⁹, R^(9′), R¹⁰ and R^(10′)each being hydrogen,C₁-C₁₀-alkyl or carboxylate and the groups R¹¹, R¹², R¹³ and R¹⁴ eachbeing hydrogen, C₁-C₁₀-alkyl, halogen, in particular fluorine, chlorineor bromine, trifluoromethyl, C₁-C₄-alkoxy, carboxylate, sulfonate orC₁-C₈-aryl. R⁹, R^(9′), R¹⁰, R^(10′), R¹¹, R¹², R¹³ and R¹⁴ areparticularly preferably each hydrogen. For use in an aqueous reactionmedium, preference is given to chelating pnicogen compounds in which 1,2 or 3, preferably 1 or 2, in particular 1, of the groups R¹¹, R¹², R¹³and/or R¹⁴ are a COO⁻M⁺, SO₃ ⁻M⁺or (NE¹E²E³)⁺X⁻group, where M⁺and X⁻areas defined above.

Particularly preferred bridging groups D are the ethylene group

and the 1,2-phenylene group

In the bridging groups Y of the formulae IV.a and IV.b, the substituentsR^(I), R^(II), R^(III), R^(IV), R^(V) and R^(VI) are preferably selectedfrom among hydrogen, alkyl, alkoxy, cycloalkyl, heterocycloalkyl, aryland hetaryl. In a first preferred embodiment, R^(I), R^(II), R^(III),R^(IV), R^(V) and R^(VI) are each hydrogen. In a further preferredembodiment, R^(I) and R^(V) are each, independently of one another,C₁-C₄-alkyl or C₁-C₄-alkoxy. R^(I) and R^(VI) are preferably selectedfrom among methyl, ethyl, isopropyl, tert-butyl and methoxy. In thesecompounds, R^(II), R^(III), R^(IV) and R^(V) are preferably eachhydrogen. In a further preferred embodiment, R^(II) and R^(V) are each,independently of one another, C₁-C₄-alkyl or C₁-C₄-alkoxy. R^(II) andR^(V) are preferably selected from among methyl, ethyl, isopropyl andtert-butyl. In these compounds, R^(I), R^(III), R^(IV) and R^(VI) arepreferably each hydrogen.

When two adjacent radicals selected from among R^(I), R^(II), R^(III),R^(IV), R^(V) and R^(VI) in the bridging groups Y of the formulae IV.aand IV.b form a fused-on ring system, this is preferably a benzene ringor naphthalene unit. Fused-on benzene rings are preferably unsubstitutedor have 1, 2 or 3, in particular 1 or 2, substituents selected fromamong alkyl, alkoxy, halogen, SO₃H, sulfonate, NE¹E², alkylene-NE¹E²,trifluoromethyl, nitro, COOR^(f), alkoxycarbonyl, acyl and cyano.Fused-on naphthalene units are preferably unsubstituted or have a totalof 1, 2 or 3, in particular 1 or 2, of the substituents mentioned abovein the case of the fused-on benzene rings in the ring which is not fusedon and/or in the fused-on ring.

Preference is given to Y being a group of the formula IV.c in whichR^(IV) and R^(V) are each, independently of one another, C₁-C₄-alkyl orC₁-C₄-alkoxy. R^(IV) and R^(V) are preferably selected from amongmethyl, ethyl, isopropyl, tert-butyl and methoxy. In these compoundsR^(I), R^(II), R^(III), R^(VI), R^(VII) and R^(VIII) are preferably eachhydrogen.

Preference is also given to Y being a group of the formula IV.c in whichR^(I) and R^(VIII) are each, independently of one another, C₁-C₄-alkylor C₁-C₄-alkoxy. R^(I)and R^(VIII) are particularly preferably eachtert-butyl. In these compounds, R^(II), R^(III), R^(IV), R^(V), R^(VI),R^(VII) are particularly preferably each hydrogen. Preference is alsogiven to R^(III) and R^(VI) in these compounds each being, independentlyof one another, C₁-C₄-alkyl or C₁-C₄-alkoxy. R^(III) and R^(VI) areparticularly preferably selected independently from among methyl, ethyl,isopropyl, tert-butyl and methoxy.

Preference is also given to Y being a group of the formula IV.c in whichR^(II) and R^(VII) are each hydrogen. In these compounds R^(I), R^(III),R^(IV), R^(V), R^(VI) and R^(VIII) are preferably each, independently ofone another, C₁-C₄-alkyl or C₁-C₄-alkoxy. R^(I), R^(III), R^(IV), R^(V),R^(VI) and R^(VIII) are particularly preferably selected independentlyfrom among methyl, ethyl, isopropyl, tert-butyl and methoxy.

Furthermore, preference is given to Y being a group of the formula IV.din which Z is a C₁-C₄-alkylene group, in particular methylene. In thesecompounds, R^(IV) and R^(V) are preferably each, independently of oneanother, C₁-C₄-alkyl or C₁-C₄-alkoxy. R^(IV) and R^(V) are particularlypreferably selected independently from among methyl, ethyl, isopropyl,tert-butyl and methoxy. The radicals R^(I), R^(II), R^(III), R^(VI),R^(VII) and R^(VIII) are preferably each hydrogen.

Preference is also given to Y being a group of the formula IV.d in whichZ is a C₁-C₄-alkylene bridge bearing at least one alkyl, cycloalkyl oraryl radical. Z is particularly preferably a methylene bridge bearingtwo C₁-C₄-alkyl radicals, in particular two methyl radicals. In thesecompounds, the radicals R^(I) and R^(VIII) are preferably each,independently of one another, C₁-C₄-alkyl or C₁-C₄-alkoxy. R^(I) andR^(VIII) are particularly preferably selected independently from amongmethyl, ethyl, isopropyl, tert-butyl and methoxy.

Furthermore, preference is given to Y being a group of the formula IV.ein which R^(I) and R^(XII) are each, independently of one another,C₁-C₄-alkyl or C₁-C₄-alkoxy. In particular, R^(I) and R^(XII) areselected independently from among methyl, ethyl, isopropyl, tert-butyl,methoxy and alkoxycarbonyl, preferably methoxycarbonyl. In thesecompounds, the radicals R^(II) to R^(XI) are particularly preferablyeach hydrogen.

Preference is also given to Y being a group of the formula IV.f in whichR^(I) and R^(XII) are each, independently of one another, C₁-C₄-alkyl orC₁-C₄-alkoxy. In particular, R^(I) and R^(XII) are selectedindependently from among methyl, ethyl, isopropyl, tert-butyl andmethoxy. In these compounds, the radicals R^(II) to R^(XI) areparticularly preferably each hydrogen.

Furthermore, preference is given to Y being a group of the formula IV.gin which Z is a C₁-C₄-alkylene group bearing at least one alkyl,cycloalkyl or aryl substituent. Z is particularly preferably a methylenegroup bearing two C₁-C₄-alkyl radicals, especially two methyl radicals.In these compounds, the radicals R^(I) and R^(VIII) are particularlypreferably each, independently of one another, C₁-C₄-alkyl orC₁-C₄-alkoxy. In particular, R^(I)and R^(VIII) are selectedindependently from among methyl, ethyl, isopropyl, tert-butyl andmethoxy. The radicals R^(II), R^(III), R^(IV), R^(V), R^(VI) and R^(VII)are preferably each hydrogen.

Preference is also given to Y being a group of the formula IV.h in whichR^(I), R^(I′), R^(II), R^(II′), R^(III) and R^(III′)are each hydrogen.

Preference is also given to Y being a group of the formula IV.h in whichR^(II) and R^(II′) together represent an oxo group or a ketal thereofand the other radicals are each hydrogen.

Preference is also given to Y being a group of the formula IV.i in whichR^(I), R^(I′), R^(II), R^(II′), R^(III) and R^(III′)are each hydrogen.

Preference is also given to Y being a group of the formula IV.i in whichR^(II) and R^(II′)together represent an oxo group or a ketal thereof andthe other radicals are each hydrogen.

Preference is also given to Y being a group of the formula IV.k in whichR^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV) and R^(IV′)areeach hydrogen.

Preference is also given to Y being a group of the formula IV.l in whichR^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV) and R^(IV′)areeach hydrogen.

Preference is also given to Y being a group of the formula IV.m in whichR^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV) and R^(IV′)areeach hydrogen.

Preference is also given to Y being a group of the formula IV.n in whichR^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV) and R^(IV′)areeach hydrogen.

Preference is also given to Y being a group of the formula IV.o in whichR^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV) and R^(IV′)areeach hydrogen.

Preference is also given to Y being a group of the formula IV.o in whichone of the radicals R^(I) to R^(IV) is C₁-C₄-alkyl or C₁-C₄-alkoxy.Particular preference is then given to at least one of the radicalsR^(I) to R^(IV) being methyl, ethyl, isopropyl, tert-butyl or methoxy.

Preference is also given to Y being a group of the formula IV.p in whichR^(I), R^(II), R^(III) and R^(IV) are each hydrogen.

Preference is also given to Y being a group of the formula IV.p in whichone of the radicals R^(I), R^(II), R^(III) or R^(IV) is C₁-C₄-alkyl orC₁-C₄-alkoxy. Particular preference is then given to one of the radicalsR^(I) to R^(IV) being methyl, ethyl, tert-butyl or methoxy.

Preference is also given to Y being a group of the formula IV.q in whichR^(I) and R^(VI) are each, independently of one another, C₁-C₄-alkyl orC₁-C₄-alkoxy. R^(I) and R^(VI) are particularly preferably selectedindependently from among methyl, ethyl, isopropyl, tert-butyl andmethoxy. In these compounds, R^(II), R^(III), R^(IV) and R^(V) areparticularly preferably each hydrogen. Preference is also given toR^(I), R^(III), R^(IV) and R^(VI) in the compounds IV.q each being,independently of one another, C₁-C₄-alkyl or C₁-C₄-alkoxy. Particularpreference is then given to R^(I), R^(III), R^(IV) and R^(VI) beingselected independently from among methyl, ethyl, isopropyl, tert-butyland methoxy.

Preference is also given to Y being a group of the formula IV.r in whichR^(I) and R^(VI) are each, independently of one another, C₁-C₄-alkyl orC₁-C₄-alkoxy. R^(I) and R^(VI) are particularly preferably selectedindependently from among methyl, ethyl, isopropyl, tert-butyl andmethoxy. In these compounds, R^(II), R^(III), R^(IV) and R^(V) areparticularly preferably each hydrogen. Preference is also given toR^(III) and R^(IV) in these compounds each being, independently of oneanother, C₁-C₄-alkyl or C₁-C₄-alkoxy. Particular preference is thengiven to R^(III) and R^(IV) being selected independently from amongmethyl, ethyl, isopropyl, tert-butyl and methoxy.

Preference is also given to Y being a group of the formula IV.s, IV.t orIV.u in which Z is CH₂, C₂H₂ or C₂H₄.

In the compounds of the formulae IV.s, IV.t and IV.u, the indicatedbonds to the bridged groups can equally well be in the endo and exopositions.

The catalysts used according to the invention can further comprise atleast one additional ligand which is preferably selected from amonghalides, amines, carboxylates, acetylacetonate, arylsulfonates andalkylsulfonates, hydride, CO, olefins, dienes, cycloolefins, nitriles,N-containing heterocycles, aromatics and heteroaromatics, ethers, PF₃,phospholes, phosphabenzenes, monodentate, bidentate and polydentatephosphine, phosphinite, phosphonite, phosphite ligands and mixturesthereof.

In general, the catalysts or catalyst precursors used in each case areconverted under hydroformylation conditions into catalytically activespecies of the formula H_(t)M_(u)(CO)_(v)L_(w), where M is a metal oftransition group VIII, L is a phosphoramidite compound and t, u, v, ware integers which depend on the valence and type of the metal and onthe number of coordination sites occupied by the ligand L. It ispreferred that v and w each have, independently of one another, a valueof at least 1, e.g. 1, 2 or 3. The sum of v and w is preferably from 1to 5. If desired, the complexes may further comprise at least one of theabove-described additional ligands.

In a preferred embodiment, the hydroformylation catalysts are preparedin situ in the reactor used for the hydroformylation reaction. However,the catalysts used according to the invention can, if desired, also beprepared separately and isolated by customary methods. For the in-situpreparation of the catalysts used according to the invention, it ispossible, for example, to react at least one phosphoramidite compound, acompound or a complex of a metal of transition group VIII, ifappropriate at least one further additional ligand and, if appropriate,an activating agent in an inert solvent under the hydroformylationconditions.

Suitable rhodium compounds or complexes are, for example, rhodium(II)and rhodium(III) salts such as rhodium(II) chloride, rhodium(III)nitrate, rhodium(III) sulfate, potassium rhodium sulfate, rhodium(II) orrhodium(III) carboxylate, rhodium(II) and rhodium(III) acetate,rhodium(II) and rhodium(III) ethylhexanoate, rhodium(III) oxide, saltsof rhodic(III) acid, trisammonium hexachlororhodate(III), etc. Alsosuitable are rhodium complexes such as dicarbonylrhodiumacetylacetonate, acetylacetonato-bisethylenerhodium(I), etc. Preferenceis given to using dicarbonylrhodium acetylacetonate or rhodium acetate.

Likewise suitable are ruthenium salts or compounds. Suitable rutheniumsalts are, for example, ruthenium(III) chloride, ruthenium(IV),ruthenium(VI) or ruthenium(VIII) oxide, alkali metal salts of rutheniumoxo acids such as K₂RuO₄ or KRuO₄ or complexes such as RuHCl(CO)(PPh₃)₃.It is also possible to use the metal carbonyls of ruthenium, for exampledodecacarbonyltriruthenium or octadecacarbonylhexaruthenium, or mixedforms in which CO is partly replaced by ligands of the formula PR₃, e.g.Ru(CO)₃(PPh₃)₂, in the process of the invention.

Suitable cobalt compounds are, for example, cobalt(II) chloride,cobalt(II) sulfate, cobalt(II) carbonate, cobalt(II) nitrate, theiramine or hydrate complexes, cobalt carboxylates, such as cobalt acetate,cobalt ethylhexanoate, cobalt naphthanoate, and also the cobalt caproatecomplex. Here too, the carbonyl complexes of cobalt such as octacarbonyldicobalt, dodecacarbonyl tetracobalt and hexadecacarbonyl hexacobalt canbe used.

The abovementioned and further suitable compounds of cobalt, rhodium,ruthenium and iridium are known in principle and are adequatelydescribed in the literature or can be prepared by a person skilled inthe art by methods analogous to those for the known compounds.

Suitable activating agents are, for example, Bronsted acids, Lewisacids, e.g. BF₃, AlCl₃, ZnCl₂, SnCl₂ and Lewis bases.

Suitable starting olefins for the process of the invention are inprinciple all compounds which contain one or more ethylenicallyunsaturated double bonds. These include olefins having terminal orinternal double bonds, straight-chain or branched olefins, cyclicolefins and also olefins which bear substituents which are essentiallyinert under the hydroformylation conditions. Preference is given tostarting olefins comprising olefins having from 4 to 12, particularlypreferably from 4 to 6, carbon atoms. The olefins used for thehydroformylation are preferably selected from among linear(straight-chain) olefins and olefin mixtures comprising at least onelinear olefin. The process of the invention makes it possible tohydroformylate, in particular, linear α-olefins, linear internal olefinsand mixtures of linear α-olefins and linear internal olefins.

α-Olefins preferred as substrates for the hydroformylation process ofthe invention are C₄-C₂₀-α-olefins, e.g. 1-butene, isobutene, 1-pentene,2-methyl-1-butene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene,1-undecene, 1-dodecene, allyl alcohols, etc.

Preference is given to linear α-olefins and olefin mixtures comprisingat least one linear α-olefin.

The unsaturated compound used for the hydroformylation is preferablyselected from among internal linear olefins and olefin mixturescomprising at least one internal linear olefin. Preferred linearinternal olefins are C₄-C₂₀-olefins, such as 2-butene, 2-pentene,2-hexene, 3-hexene, 2-heptene, 3-heptene, 2-octene, 3-octene, 4-octene,etc., and mixtures thereof.

Preferred branched, internal olefins are C₄-C₂₀-olefins such as2-methyl-2-butene, 2-methyl-2-pentene, 3-methyl-2-pentene, branched,internal heptene mixtures, branched, internal octene mixtures, branched,internal nonene mixtures, branched, internal decene mixtures, branched,internal undecene mixtures, branched, internal dodecene mixtures, etc.

Further olefins suitable for the hydroformylation process areC₅-C₈-cycloalkenes, such as cyclopentene, cyclohexene, cycloheptene,cyclooctene and derivatives thereof, e.g.

their C₁-C₂₀-alkyl derivatives having from 1 to 5 alkyl substituents.Other olefins suitable for the hydroformylation process arevinylaromatics such as styrene, α-methylstyrene, 4-isobutylstyrene, etc.Olefins suitable for the hydroformylation process additionally includeα,β-ethylenically unsaturated monocarboxylic and/or dicarboxylic acids,their esters, semiesters and amides, e.g. acrylic acid, methacrylicacid, maleic acid, fumaric acid, crotonic acid, itaconic acid, methyl3-pentenoate, methyl 4-pentenoate, methyl oleate, methyl acrylate andmethyl methacrylate. Further olefins suitable for the hydroformylationprocess are unsaturated nitriles, such as 3-pentenenitrile,4-pentenenitrile and acrylonitrile. Further olefins suitable for thehydroformylation process are vinyl ethers, e.g. vinyl methyl ether,vinyl ethyl ether, vinyl propyl ether, etc. Other olefins suitable forthe hydroformylation process are alkenols, alkenediols and alkadienolssuch as 2,7-octadien-1-ol. Further olefins suitable for thehydroformylation process are dienes or polyenes having isolated orconjugated double bonds. These include, for example, 1,3-butadiene,1,4-pentadiene, 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene,1,9-decadiene, vinylcyclohexene, dicyclopentadiene,1,5,9-cyclooctatriene, homopolymers and copolymers of butadiene and alsoolefins having terminal and internal double bonds, e.g. 1,4-octadiene.

The hydroformylation process of the invention is preferably carried outusing an industrially available olefin-containing hydrocarbon mixture.

Preferred olefin mixtures which are available on an industrial scaleresult from the cracking of hydrocarbons in petroleum processing, forexample by catalytic cracking such as fluid catalytic cracking (FCC),thermal cracking or hydrocracking with subsequent dehydrogenation. Onesuitable industrial olefin mixture is a C₄ fraction. C₄ fractions can beobtained, for example, by fluid catalytic cracking or steam cracking ofgas oil or by steam cracking naphtha. Depending on the composition ofthe C₄ fraction, a distinction is made between the total C₄ fraction(raw C₄ fraction), the raffinate I obtained after 1,3-butadiene has beenseparated off and also the raffinate II obtained after the isobutene hasbeen separated off. A further suitable industrial olefin mixture is theC₅ fraction obtainable in the cracking of naphtha. Olefin-containinghydrocarbon mixtures containing compounds having from 4 to 6 carbonatoms which are suitable for use in step a) can also be obtained bycatalytic dehydrogenation of suitable industrially available paraffinmixtures. Thus, for example, C₄ olefin mixtures can be produced fromliquefied petroleum gas (LPG) and liquefied natural gas (LNG). Thelatter comprises, in addition to the LPG fraction, relatively largeamounts of high molecular weight hydrocarbons (light naphtha) and isthus also suitable for preparing C₅- and C₆-olefin mixtures.Olefin-containing hydrocarbon mixtures comprising monoolefins havingfrom 4 to 6 carbon atoms can be prepared from LPG or LNG streams byconventional methods known to those skilled in the art which, inaddition to dehydrogenation, generally comprise one or more work-upsteps. Such steps include, for example, the removal of at least part ofthe saturated hydrocarbons present in the abovementioned olefin feedmixtures. The saturated hydrocarbons can, for example, be reused for thepreparation of starting olefins by cracking and/or dehydrogenation.However, the olefins used in the process of the invention can alsocontain a proportion of saturated hydrocarbons which are inert under thehydroformylation conditions of the invention. The proportion of thesesaturated components is generally not more than 60% by weight,preferably not more than 40% by weight, particularly preferably not morethan 20% by weight, based on the total amount of olefins and saturatedhydrocarbons present in the hydrocarbon starting material.

A raffinate II suitable for use in the process of the invention has, forexample, the following composition:

-   from 0.5 to 5% by weight of isobutane,-   from 5 to 20% by weight of n-butane,-   from 20 to 40% by weight of trans-2-butene,-   from 10 to 20% by weight of cis-2-butene,-   from 25 to 55% by weight of 1-butene,-   from 0.5 to 5% by weight of isobutene    and also trace gases such as 1,3-butadiene, propene, propane,    cyclopropane, propadiene, methylcyclopropane, vinylacetylene,    pentenes, pentanes, etc., in concentrations of not more than 1% by    weight in each case.

It has surprisingly been found that catalytically active fluids based onmetal complexes of phosphoramidite compounds can be additionallystabilized by bringing them into contact with a base. Thus, longercatalyst operating lives are achieved in the process of the inventionthan in hydroformylation processes known from the prior art which usecatalysts based either on conventional monodentate and polydentateligands or, in particular, based on phosphoramidite ligands. Thecatalytic activity is generally not adversely affected by contactingwith the base.

The invention further provides a method of stabilizing a catalyticallyactive fluid comprising a dissolved metal complex of a metal oftransition group VIII of the Periodic Table of the Elements with atleast one phosphoramidite compound as ligand in the hydroformylation ofethylenically unsaturated compounds, which comprises bringing the fluidinto contact with a base.

The invention also provides for the use of bases for stabilizing acatalytically active fluid comprising a dissolved metal complex of ametal of transition group VIII of the Periodic Table of the Elementswith at least one phosphoramidite compound as ligand in thehydroformylation of ethylenically unsaturated compounds.

The invention is illustrated by the following nonrestrictive examples.

EXAMPLES

1. Preparation of the Compound (1)

28.5 g (218 mmol) of 3-methylindole (skatole) together with about 50 mlof dried toluene were placed in a reaction vessel and the solvent wasdistilled off under reduced pressure to remove traces of water byazeotropic distillation. This procedure was repeated once more. Theresidue was subsequently taken up in 700 ml of dried toluene under argonand cooled to −65° C. 14.9 g (109 mmol) of PCl₃ followed by 40 g (396mmol) of triethylamine were then added slowly at −65° C. The reactionmixture was brought to room temperature over a period of 16 hours andthen refluxed for 16 hours. 19.3 g (58 mmol) of4,5-dihydroxy-2,7-di-tert-butyl-9,9-dimethylxanthene in 300 ml of driedtoluene were added to the reaction mixture, the mixture was thenrefluxed for 16 hours and, after cooling to room temperature, thecolorless solid which had precipitated (triethylamine hydrochloride) wasfiltered off with suction, the solvent was distilled off and the residuewas recrystallized twice from hot ethanol. Drying under reduced pressuregave 36.3 g (71% of theory) of a colorless solid.

³¹P-NMR (298K): δ=105 ppm.

2. Hydroformylation of Trans-2-butene without Additive (ComparativeExample)

0.005 g of Rh(CO)₂(acac) and 0.181 g of the compound (1) were dissolvedin 10.17 g of xylene under a protective gas atmosphere and the mixturewas transferred to a 100 ml steel autoclave. The autoclave waspressurized with 10 bar of synthesis gas (CO/H₂=1:2) and then heated to90° C. over a period of one hour. The autoclave was then carefullydepressurized to 7 bar at 90° C., and 10.81 g of a liquefied gas mixture(30% by volume of trans-2-butene and 70% by volume of isobutane) wereinjected via a lock by means of synthesis gas of the abovementionedcomposition (p=12 bar). The pressure was then set to 16 bar (total) bymeans of the synthesis gas. During the reaction time of 4 hours, thetemperature was kept at 90° C. and the pressure was maintained at 16 bar(total) by addition of CO/H₂ (1:1). After the reaction was complete, theautoclave was depressurized via a cold trap and the contents of theautoclave and of the cold trap were analyzed by gas chromatography inorder to determine the conversion, the yield of pentanals and theproportion of n-valeraldehyde among the pentanals.

Results of the analysis by gas chromatography:

Conversion 32% Yield 31% Proportion of n product 93%3. Degradation Experiment with Addition of N,N-dimethylaniline

0.005 g of Rh(CO)₂(acac), 0.181 g of compound (1) and 0.26 g ofN,N-dimethylaniline were dissolved in 8.12 g of Texanole®(2,2,4-trimethyl-1,3-pentanediol monobutyrate, from Eastman) under aprotective gas atmosphere and the mixture was transferred to a 60 mlsteel autoclave. The autoclave was pressurized at 25° C. with 20 bar ofCO/H₂ (1:1) and heated to 120° C. over a period of 60 minutes. Theautoclave was then carefully depressurized to 7 bar at 120° C. and 11.23g of a liquefied gas mixture (2.9% by volume of isobutane; 14.6% byvolume of n-butane; 27.4% by volume of trans-2-butene; 37.4% by volumeof 1-butene; 2.6% by volume of isobutene; 15.3% of cis-2-butene) wereinjected via a lock by means of CO/H₂ (1:1) at 12 bar. The pressure wasincreased to 28 bar (total) by means of CO/H₂ (1:1) and the autoclavewas maintained at 120° C. for 24 hours. After the end of the reactiontime, the autoclave was cooled, depressurized and a sample for ³¹P-NMRanalysis was taken under a protective gas atmosphere to determine thedegree to which the ligand had been degraded.

Integration of the ³¹P-NMR spectrum indicated that 18% of the compound(1) had been degraded.

The mixture was subsequently returned to the autoclave, the autoclavewas flushed three times with nitrogen and then maintained at 120° C. anda nitrogen pressure of 3 bar for 24 hours to simulate long-termstressing of the catalyst as occurs in prolonged continuous operation.After the end of the reaction time, the autoclave was cooled,depressurized and a sample for ³¹P-NMR analysis was taken under aprotective gas atmosphere in order to determine the degree to which theligand had been degraded.

Integration of the ³¹P-NMR spectrum indicated that a total of only 42%of the compound (1) had been degraded.

4. Hydroformylation of Trans-2-butene with Addition ofN,N-dimethylaniline

0.005 g of Rh(CO)₂(acac), 0.181 g of the compound (1) and 0.025 g ofN,N-dimethyl-aniline were dissolved in 10.17 g of xylene under aprotective gas atmosphere and the mixture was transferred to a 100 mlsteel autoclave. The autoclave was pressurized with 10 bar of CO/H₂(1:2) and was then heated to 90° C. over a period of 1 hour. Theautoclave was then carefully depressurized to 7 bar at 90° C. and 10.81g of a liquefied gas mixture (30% by volume of trans-2-butene and 70% byvolume of isobutane) were injected via a lock by means of CO/H₂ (1:2) at12 bar and the pressure was set to 16 bar (total) by means of CO/H₂(1:2). During the reaction time of 4 hours, the temperature was kept at90° C. and the pressure was maintained at 16 bar (total) by means ofCO/H₂ (1:1). After the end of the reaction, the autoclave wasdepressurized via a cold trap and the contents of the autoclave and ofthe cold trap were analyzed by gas chromatography in order to determinethe conversion, the yield of pentanals and the proportion ofn-valeraldehyde among the pentanals.

Results of the analysis by gas chromatography:

Conversion 30% Yield 28% Proportion of n product 94%

Conversion, yield and proportion of n product were not reducedsignificantly compared to comparative example 2 by addition of the base.

5. Degradation Experiment with Addition of N,N,2,4,6-pentamethylaniline

0.005 g of Rh(CO)₂(acac), 0.181 g of compound (1) and 0.35 g ofN,N,2,4,6-penta-methylaniline were dissolved in 8.11 g of Texanol undera protective gas atmosphere and the mixture was transferred to a 60 mlsteel autoclave. The autoclave was pressurized with 20 bar of CO/H₂(1:1) at 25° C. and was then heated to 120° C. over a period of 60minutes. The autoclave was then carefully depressurized to 7 bar at 120°C. and 11.23 g of a liquefied gas mixture (2.9% by volume of isobutane;14.6% by volume of n-butane; 27.4% by volume of trans-2-butene; 37.4% byvolume of 1-butene; 2.6% by volume of isobutene; 15.3% of cis-2-butene)were then injected via a lock by means of CO/H₂ (1:1) at 12 bar. Thepressure was increased to 28 bar (total) by means of CO/H₂ (1:1) and theautoclave was maintained at 120° C. for 24 hours.

After the end of the reaction time, the autoclave was cooled,depressurized and a sample for ³¹P-NMR analysis was taken under aprotective gas atmosphere to determine the degree to which the ligandhad been degraded.

Integration of the ³¹P-NMR spectrum indicated that 4% of the compound(1) had been degraded.

The mixture was subsequently returned to the autoclave, the autoclavewas flushed three times with nitrogen and then maintained at 120° C. anda nitrogen pressure of 3 bar for 24 hours. After the end of the reactiontime, the autoclave was cooled, depressurized and a sample for ³¹P-NMRanalysis was taken under a protective gas atmosphere in order todetermine the degree to which the ligand had been degraded.

Integration of the ³¹P-NMR spectrum indicated that a total of 23% of thecompound (1) had been degraded.

6. Hydroformylation of Trans-2-butene with Addition ofN,N,2,4,6-pentamethylaniline

0.005 g of Rh(CO)₂(acac), 0.181 g of the compound (1) and 0.035 g ofN,N,2,4,6-pentamethylaniline were dissolved in 10.26 g of xylene under aprotective gas atmosphere and the mixture was transferred to a 100 mlsteel autoclave. The autoclave was pressurized with 10 bar of CO/H₂(1:2) and was then heated to 90° C. over a period of 1 hour. Theautoclave was then carefully depressurized to 7 bar at 90° C. and 10.81g of a liquefied gas mixture (30% by volume of trans-2-butene and 70% byvolume of isobutane) were injected via a lock by means of CO/H₂ (1:2) at12 bar and the pressure was set to 16 bar (total) by means of CO/H₂(1:2). During the reaction time of 4 hours, the temperature was kept at90° C. and the pressure was maintained at 16 bar (total) by means ofCO/H₂ (1:1). After the end of the reaction, the autoclave wasdepressurized via a cold trap and the contents of the autoclave and ofthe cold trap were analyzed by gas chromatography in order to determinethe conversion, the yield of pentanals and the proportion ofn-valeraldehyde among the pentanals.

Results of the analysis by gas chromatography:

Conversion 29% Yield 28% Proportion of n product 93%7. Hydroformylation of Trans-2-butene with Addition of 3-methylindole

0.005 g of Rh(CO)₂(acac), 0.180 g of the compound (1) and 0.10 g of3-methylindole were dissolved in 10.14 g of xylene under a protectivegas atmosphere and the mixture was transferred to a 100 ml steelautoclave. The autoclave was pressurized with 10 bar of CO/H₂ (1:2) andwas then heated to 90° C. over a period of 1 hour. The autoclave wasthen carefully depressurized to 7 bar at 90° C. and 10.81 g of aliquefied gas mixture (30% by volume of trans-2-butene and 70% by volumeof isobutane) were injected via a lock by means of CO/H₂ (1:2) at 12 barand the pressure was set to 16 bar (total) by means of CO/H₂ (1:2).During the reaction time of 4 hours, the temperature was kept at 90° C.and the pressure was maintained at 16 bar (total) by means of CO/H₂(1:1). After the end of the reaction, the autoclave was depressurizedvia a cold trap and the contents of the autoclave and of the cold trapwere analyzed by gas chromatography in order to determine theconversion, the yield of pentanals and the proportion of n-valeraldehydeamong the pentanals.

Results of the analysis by gas chromatography:

Conversion 33% Yield 32% Proportion of n product 94%8. Hydroformylation of Trans-2-butene with Addition of Quinoline

0.005 g of Rh(CO)₂(acac), 0.181 g of the compound (1) and 0.029 g ofquinoline were dissolved in 10.16 g of xylene under a protective gasatmosphere and the mixture was transferred to a 100 ml steel autoclave.The autoclave was pressurized with 10 bar of CO/H₂ (1:2) and was thenheated to 90° C. over a period of 1 hour. The autoclave was thencarefully depressurized to 7 bar at 90° C. and 10.81 g of a liquefiedgas mixture (30% by volume of trans-2-butene and 70% by volume ofisobutane) were injected via a lock by means of CO/H₂ (1:2) at 12 barand the pressure was set to 16 bar (total) by means of CO/H₂ (1:2).During the reaction time of 4 hours, the temperature was kept at 90° C.and the pressure was maintained at 16 bar (total) by means of CO/H₂(1:1). After the end of the reaction, the autoclave was depressurizedvia a cold trap and the contents of the autoclave and of the cold trapwere analyzed by gas chromatography in order to determine theconversion, the yield of pentanals and the proportion of n-valeraldehydeamong the pentanals.

Results of the analysis by gas chromatography:

Conversion 29% Yield 27% Proportion of n product 90%9. Hydroformylation of Raffinate II without Additive (ComparativeExample)

0.006 g of Rh(CO)₂(acac) and 0.217 g of the compound (1) were dissolvedin 10.0 g of toluene under a protective gas atmosphere and the mixturewas transferred to a 100 ml steel autoclave. The autoclave waspressurized with 10 bar of CO/H₂ (1:2) and was then heated to 90° C.over a period of 0.5 hour. The autoclave was then carefullydepressurized to 7 bar at 90° C. and 10.2 g of a liquefied gas mixture(1.7% of isobutane, 12.4% of n-butane, 31.7% of trans-2-butene, 35.1% of1-butene, 2.4% of isobutene, 16.8% of cis-2-butene) were injected via alock by means of CO/H₂ (1:2) at 12 bar and the pressure was set to 17bar (total) by means of CO/H₂ (1:2). During the reaction time of 4hours, the temperature was kept at 90° C. and the pressure wasmaintained at 17 bar (total) by means of CO/H₂ (1:1). After the end ofthe reaction, the autoclave was depressurized via a cold trap and thecontents of the autoclave and of the cold trap were analyzed by gaschromatography in order to determine the conversion, the yield ofpentanals and the proportion of n-valeraldehyde among the pentanals.

Results of the analysis by gas chromatography:

Conversion 89% Yield 88% Proportion of n product 95%10. Hydroformylation of Raffinate II with Addition of 1-H-benzotriazole

0.006 g of Rh(CO)₂(acac) and 0.212 g of the compound (1) and 0.014 g of1-H-benzotriazole were dissolved in 10.1 g of toluene under a protectivegas atmosphere and the mixture was transferred to a 100 ml steelautoclave. The autoclave was pressurized with 10 bar of CO/H₂ (1:2) andwas then heated to 90° C. over a period of 0.5 hour. The autoclave wasthen carefully depressurized to 7 bar at 90° C. and 10.4 g of aliquefied gas mixture (1.7% of isobutane, 12.4% of n-butane, 31.7% oftrans-2-butene, 35.1% of 1-butene, 2.4% of isobutene, 16.8% ofcis-2-butene) were injected via a lock by means of CO/H₂ (1:2) at 12 barand the pressure was set to 17 bar (total) by means of CO/H₂ (1:2).During the reaction time of 4 hours, the temperature was kept at 90° C.and the pressure was maintained at 17 bar (total) by means of CO/H₂(1:1). After the end of the reaction, the autoclave was depressurizedvia a cold trap and the contents of the autoclave and of the cold trapwere analyzed by gas chromatography in order to determine theconversion, the yield of pentanals and the proportion of n-valeraldehydeamong the pentanals.

Results of the analysis by gas chromatography:

Conversion 88% Yield 87% Proportion of n product 95%(no significant change compared to comparative example 9)11. Degradation Experiment Using 1-H-benzotriazole

0.005 g of Rh(CO)₂(acac), 0.181 g of compound (1) and 0.024 g of1-H-benzotriazole were dissolved in 8.02 g of Texanole® under aprotective gas atmosphere and the mixture was transferred to a 60 mlsteel autoclave. The autoclave was pressurized at 25° C. with 20 bar ofCO/H₂ (1:1) and then heated to 120° C. over a period of 60 minutes. Theautoclave was then carefully depressurized to 7 bar at 120° C. and 11.23g of a liquefied gas mixture (2.9% by volume of isobutane; 14.6% byvolume of n-butane; 27.4% by volume of trans-2-butene; 37.4% by volumeof 1-butene; 2.6% by volume of isobutene; 15.3% of cis-2-butene) wereinjected via a lock by means of CO/H₂ (1:1) at 12 bar. The pressure wasincreased to 28 bar (total) by means of CO/H₂ (1:1) and the autoclavewas maintained at 120° C. for 24 hours. After the end of the reactiontime, the autoclave was cooled, depressurized and a sample for ³¹P-NMRanalysis was taken under a protective gas atmosphere to determine thedegree to which the ligand had been degraded.

Integration of the ³¹P-NMR spectrum indicated that 3% of the compound(1) had been degraded.

The mixture was subsequently returned to the autoclave, the autoclavewas flushed three times with nitrogen and then maintained at 120° C. anda nitrogen pressure of 3 bar for 24 hours. After the end of the reactiontime, the autoclave was cooled, depressurized and a sample for ³¹P-NMRanalysis was taken under a protective gas atmosphere in order todetermine the degree to which the ligand had been degraded.

Integration of the ³¹P-NMR spectrum indicated that a total of 29% of thecompound (1) had been degraded.

12. Hydroformylation of Raffinate II and Treatment of the ReactionProduct Mixture with an Ion Exchanger

0.0051 g of Rh(CO)₂(acac) (acac =acetylacetonate) and 0.1806 g of ligand(1) were dissolved in 8.05 g of toluene under N₂. This solution wasanalyzed by ³¹P-NMR (see table 1; blank) and the mixture was transferredto a 100 ml steel autoclave. The autoclave was pressurized with 20 barof CO/H₂ (1:1) at 25° C., and then heated to 120° C. and maintained atthis temperature for 30 minutes. The autoclave was subsequentlydepressurized to 7 bar and 11.37 g of liquefied gas mixture wereinjected via a lock by means of CO/H₂ (1:1) at 12 bar.

The liquefied gas mixture had the following composition (in % byweight):

isobutane 2.9% n-butane 14.6% trans-2-butene 27.4% 1-butene 37.4%isobutene 2.6% cis-2-butene 15.3%

The pressure in the autoclave was brought to a total pressure of 28 barby means of CO/H₂ (1:1) and these conditions were maintained for 24hours. The autoclave was subsequently cooled, depressurized and a sampleof the contents of the reactor were analyzed by ³¹P-NMR (see table 1).21.8 g of a yellow, homogeneous solution were obtained.

The product mixture was stirred with 2 g of Amberlite® IRA 67 at 25° C.under N₂ for 30 minutes.

A sample of the liquid reaction mixture was subsequently analyzed by³¹P-NMR (see table 1).

TABLE 1 Results of the ³¹P-NMR analysis: Quantitative ³¹P-NMR analysisEvaluation of the integrals in % by area Ligand Degradation Sample (1)Oxide (2) Oxide (3) products Blank 98.6 1.4 After hydroformylation 25.37.1 1.5 66.1 After treatment with 37.3 10.2 3.1 49.4 ion exchanger

The oxidation is caused by sampling. The oxides are to be counted asligand:

13. Continuous Hydroformylation without Stabilization (ComparativeExample)

FIG. 1 shows a miniplant for carrying out continuous hydroformylations.This consists of two autoclaves with lifting stirrer connected in series(1 and 2) and having a liquid capacity of 0.4 l (reactor 1) and 1.9 l(reactor 2), a pressure separator (3), a flash stripping column (4)operated using nitrogen as stripping gas for separating off thecatalyst-containing high-boiling phase from the product phase andunreacted C₄-hydrocarbons and also an ion exchanger bed (5). In thisplant, raffinate II (isobutane 2.4%, n-butane 12.6%, trans-2-butene31.5%, 1-butene 36.8%, isobutene 1.8%, cis-2-butene 14.9%) washydroformylated using rhodium and the ligand from example 1 as catalyst.The catalyst recycle stream from the flash column (4) amounted to about200 g/h and the raffinate II inflow was about 180 g/h. The temperatureof the two reactors was 90° C. The first reactor was operated usingsynthesis gas having a CO:H₂ molar ratio of 4:6 and at a total pressureof about 17 bar. Hydrogen was additionally introduced into the secondreactor and the reactor was operated at a total pressure of 16 bar. TheCO content of the offgas was set to 10%. In steady-state operation overa representative period of eight days, the plant gave an aldehyde yieldof 55%. The ion exchanger (5) was not active in this experiment. Therhodium concentration in the catalyst recycle stream from the flashcolumn (4) was about 320 ppm. According to HPLC analysis, 15 000 ppm ofskatOX ligand (1) were present in the catalyst recycle stream at thebeginning of the period of time under consideration. After six days,only 3100 ppm of skatOX ligand (1) could be detected by HPLC analysis,and after eight days no skatOX ligand (1) could be detected.

14. Continuous Hydroformylation with Stabilization by Means of an IonExchanger

FIG. 2 shows a miniplant for carrying out continuous hydroformylations.This consists of two autoclaves with lifting stirrer connected in series(1 and 2) and each having a liquid capacity of 1.9 l, a pressureseparator (3), a heated depressurization vessel for separating offC₄-hydrocarbons (4), a wiped film evaporator (5) for separating off thecatalyst-containing high-boiling phase from the product phase and an ionexchanger bed (6). In this plant, raffinate II (isobutane 3.6%, n-butane13.8%, trans-2-butene 30.9%, 1-butene 32.0%, isobutene 2.2%,cis-2-butene 17.5%) was hydroformylated using rhodium and the ligand (1)as catalyst. The catalyst recycle stream from the distillation (5)amounted to about 250 g/h and the raffinate II inflow was about 180 g/h.The temperature of the two reactors was 90° C. The reactors weresupplied with synthesis gas having a CO:H₂ molar ratio of 4:6 andoperated at a total pressure of about 17 bar. In addition, hydrogen wasintroduced into the first reactor to set the CO content of the offgas to10%. In steady-state operation over a representative period of 40 days,the plant gave an aldehyde yield of 65%. The rhodium concentration inthe stream from the separator (4) to the distillation (5) was about 110ppm. According to HPLC analysis, 7740 ppm of skatOX ligand (1) werepresent in the stream from the separator (4) to the distillation (5) atthe beginning of the period of time under consideration. After 40 days,only 2150 ppm of (1) could be detected.

15. Hydroformylation of Raffinate II with Addition of Bottoms from aPlant

0.004 g of Rh(CO)₂(acac), 0.141 g of compound (1) and 3.71 g ofcatalyst-containing bottoms from a continuously operated miniplant (asdescribed in example 13) were dissolved in 5.8 g of toluene under aprotective gas atmosphere and the mixture was transferred to a 100 mlsteel autoclave.

The bottoms came from the miniplant described in examples 13 and 14 andcontained 480 ppm of rhodium and 3800 ppm of phosphorus. The autoclavewas pressurized with 10 bar of CO/H₂ (1:2) at 25° C. and was then heatedto 90° C. over a period of 30 minutes. The autoclave was then carefullydepressurized at 90° C. and 11.6 g of a liquefied gas mixture (2.9% byvolume of isobutane; 14.6% by volume of n-butane; 27.4% by volume oftrans-2-butene; 37.4% by volume of 1-butene; 2.6% by volume ofisobutene; 15.3% of cis-2-butene) were injected via a lock by means ofCO/H₂ (1:1) at 8 bar. The pressure was increased to 17 bar (total) bymeans of CO/H₂ (1:1) and the autoclave was maintained at 90° C. for 6hours. After the end of the reaction, the autoclave was depressurizedvia a cold trap and the contents of the autoclave and of the cold trapwere analyzed by gas chromatography in order to determine theconversion, the yield of pentanals and the proportion of n-valeraldehydeamong the pentanals.

Results of the analysis by gas chromatography:

Conversion 65% Yield 59% Proportion of n product 90.7%  16. Hydroformylation of Raffinate II with Addition of Bottoms from aPlant Washing with Water

0.004 g of Rh(CO)₂(acac), 0.130 g of compound (1) and 5.37 g ofcatalyst-containing bottoms from a continuously operated miniplant (asdescribed in example 13) were dissolved in 5.37 g of toluene under aprotective gas atmosphere and the mixture was transferred to a 100 mlsteel autoclave.

The bottoms came from the miniplant described in examples 13 and 14 andcontained 480 ppm of rhodium and 3800 ppm of phosphorus. The bottomswere shaken with water under a protective gas atmosphere before use inthe experiment. The autoclave was pressurized with 10 bar of CO/H₂ (1:2)at 25° C. and was then heated to 90° C. over a period of 30 minutes. Theautoclave was then carefully depressurized at 90° C. and 9.8 g of aliquefied gas mixture (2.9% by volume of isobutane; 14.6% by volume ofn-butane; 27.4% by volume of trans-2-butene; 37.4% by volume of1-butene; 2.6% by volume of isobutene; 15.3% of cis-2-butene) wereinjected via a lock by means of CO/H₂ (1:1) at 8 bar. The pressure wasincreased to 17 bar (total) by means of CO/H₂ (1:1) and the autoclavewas maintained at 90° C. for 6 hours. After the end of the reaction, theautoclave was depressurized via a cold trap and the contents of theautoclave and of the cold trap were analyzed by gas chromatography inorder to determine the conversion, the yield of pentanals and theproportion of n-valeraldehyde among the pentanals.

Results of the analysis by gas chromatography:

Conversion 66% Yield 60% Proportion of n product 90.8%  17. Hydroformylation of Raffinate II with Addition of Bottoms from aPlant Washing with Aqueous NaHCO₃ Solution

0.003 g of Rh(CO)₂(acac), 0.104 g of compound (1) and 2.73 g ofcatalyst-containing bottoms from a continuously operated miniplant (asdescribed in example 13) were dissolved in 4.27 g of toluene under aprotective gas atmosphere and the mixture was transferred to a 100 mlsteel autoclave.

The bottoms came from the miniplant described in examples 13 and 14 andcontained 480 ppm of rhodium and 3800 ppm of phosphorus. The bottomswere shaken with aqueous NaHCO₃ solution under a protective gasatmosphere before use in the experiment. The autoclave was pressurizedwith 10 bar of CO/H₂ (1:2) at 25° C. and was then heated to 90° C. overa period of 30 minutes. The autoclave was then carefully depressurizedat 90° C. and 10.6 g of a liquefied gas mixture (2.9% by volume ofisobutane; 14.6% by volume of n-butane; 27.4% by volume oftrans-2-butene; 37.4% by volume of 1-butene; 2.6% by volume ofisobutene; 15.3% of cis-2-butene) were injected via a lock by means ofCO/H₂ (1:1) at 8 bar. The pressure was increased to 17 bar (total) bymeans of CO/H₂ (1:1) and the autoclave was maintained at 90° C. for 6hours. After the end of the reaction, the autoclave was depressurizedvia a cold trap and the contents of the autoclave and of the cold trapwere analyzed by gas chromatography in order to determine theconversion, the yield of pentanals and the proportion of n-valeraldehydeamong the pentanals.

Results of the analysis by gas chromatography:

Conversion 68% Yield 62% Proportion of n product 91.7%  

1. A process for the hydroformylation of compounds which comprises,providing at least one compound with an ethylenically unsaturated doublebond and reacting the at least one compound with carbon monoxide andhydrogen in at least one reaction zone in the presence of acatalytically active fluid which comprises a dissolved metal complex ofa metal of transition group VIII of the Periodic Table of the Elementswith at least one phosphoramidite compound as ligand, wherein the fluidis brought into contact with at least one base selected from trialkylamines, dialkyaryl amines, alkyldiaryl amines, triaryl amines, and basesimmobilized on a solid phase, or a combination thereof, and wherein thephosphoramidite compound is selected from among compounds of theformulae I and II

where R¹ and R⁵ are each, independently of one another, pyrrole groupsbound via the nitrogen atom to the phosphorus atom, R², R³ and R⁴ areeach, independently of one another, alkyl, cycloalkyl, heterocycloalkyl,aryl or hetaryl, or R¹ together with R² and/or R⁴ together with R⁵ formsa divalent group containing at least one pyrrole group bound via thepyrrolic nitrogen atom to the phosphorus atom, Y is a divalent bridgedgroup having from 2 to 20 bridge atoms between the flanking bonds, X¹,X², X³ and X⁴ are selected independently from among O, S,SiR^(α)R^(β)and NR^(γ), where R^(α), R^(β)and R^(γ)are each,independently of one another, hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl or hetaryl, and a, b, c and d are each,independently of one another, 0 or
 1. 2. A process according to claim 1,further comprising removing from the reaction zone a product mixturewhich is subjected to a fractionation to give a fraction consistingessentially of a hydroformylation product and a fraction comprising thecatalytically active fluid in which the by-products of thehydroformylation which have boiling points higher than that of thehydroformylation product are present and the metal complex is dissolved,and recirculating the catalytically active fluid to the reaction zone.3. A process according to claim 1, wherein the at least one base isselected from bases soluble in the catalytically active fluid, basesimmobilized on a solid phase or combinations thereof.
 4. A processaccording to claim 1, wherein the base comprises a basic nitrogen.
 5. Aprocess according to claim 1, wherein the at least one base is solublein the catalytic fluid and is present in a molar ratio of base tophosphoramidite compound of from 0.01:1 to 5:1, in the reaction zone. 6.A process according to claim 1, wherein the at least one base includes abase soluble in the catalytic fluid and a base immobilized on a solidphase and the immobilized base is capable of at least partly liberatingthe soluble base from acid-base adducts obtained by reaction of thesoluble base with an acid.
 7. A process according to claim 2, whereinthe fractionation of the product mixture comprises a thermal separationstep and at least one high-boiling soluble base remains in thecatalytically active fluid after the fractionation.
 8. A processaccording to claim 2, wherein at least one base immobilized on a solidphase is used and the catalytically active fluid obtained afterfractionation is brought into contact with the immobilized base beforeit is recirculated to the reaction zone.
 9. A process according to claim1, wherein the phosphoramidite compound is selected from among compoundsof the formula II.1

where R¹ and R⁵ are each, independently of one another, pyrrole groupsbound via the nitrogen atom to the phosphorus atom, R² and R⁴ are each,independently of one another, alkyl, cycloalkyl, heterocycloalkyl, arylor hetaryl, or R¹ together with R² and/or R⁴ together with R⁵ forms adivalent group containing at least one pyrrole group bound via thepyrrolic nitrogen atom to the phosphorus atom, Y is a divalent bridgedgroup having from 2 to 20 bridge atoms between the flanking bonds, and band c are each, independently of one another, 0 or
 1. 10. A processaccording to claim 1, wherein R¹, R², R⁴ and R⁵ are selectedindependently from among groups of the formulae III.a to III.k

where Alk is a C₁-C₁₂-alkyl group and R^(a), R^(b), R^(c) and R^(d) areeach, independently of one another, hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy,acyl, halogen, C₁-C₄-alkoxycarbonyl or carboxyl.
 11. A process accordingto claim 1, wherein the bridging group Y is selected from among groupsof the formulae IV.a to IV.u

where R^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV),R^(IV′), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), R^(XI) andR^(XII) are each independently of one another, hydrogen, alkyl,cycloalkyl, heterocycloalkyl, aryl, hetaryl, hydroxy, thiol,polyalkylene oxide, polyalkylenimine, alkoxy, halogen, SO₃H, sulfonate,NE¹E², alkylene-NE¹E², nitro, alkoxycarbonyl, carboxyl, acyl or cyano,where E¹ and E² are identical or different radicals selected from amonghydrogen, alkyl, cycloalkyl and aryl, Z is O, S, NR^(δ) or SiR^(δ)R^(ε),where R^(δ) and R^(ε) are each, independently of one another, hydrogen,alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl, or Z is aC₁-C₄-alkylene bridge which may have a double bond and/or bear an alkyl,cycloalkyl, heterocycloalkyl, aryl or hetaryl substituent, or Z is aC₁-C₄-alkylene bridge which may have a double bond and/or bear an alkyl,cycloalkyl, heterocycloalkyl, aryl or hetaryl substituent, or Z is aC₂-C₄-alkylene bridge which is interrupted by O, S or NR^(δ) orSiR^(δ)R^(ε), where, in the groups of the formulae IV.a and IV.b, twoadjacent radicals R^(I) to R^(VI) together with the carbon atoms of thebenzene ring to which they are bound may also form a fused ring systemhaving 1, 2 or 3 further rings, where, in the groups of the formulaeIV.h to IV.n, two geminal radicals R^(I), R^(I′); R^(II), R^(II′);R^(III), R^(III′) and/or R^(IV), R^(IV″) may also represent oxo or aketal thereof, A¹ and A² are each, independently of one another, O, S,SiR^(φ)R^(γ), NR^(η) or CR^(ι)R^(κ), where R^(φ),R^(γ), R^(η), R^(ι) andR^(κ) are each, independently of one another, hydrogen, alkyl,cycloalkyl, heterocycloalkyl, aryl or hetaryl, A³ and A⁴ are each,independently of one another, SiR, N or CR^(ι), D is a divalent bridginggroup of the formula

where R⁹, R^(9′), R¹⁰ and R^(10′) are each, independently of oneanother, hydrogen, alkyl, cycloalkyl, aryl, halogen, trifluoromethyl,carboxyl, carboxylate or cyano, where R^(9′) together with R^(10′) canalso represent the second bond of a double bond between the two carbonatoms to which R^(9′) and R^(10′) are bound, and/or R⁹ and R¹⁰ togetherwith the carbon atoms to which they are bound may also form a 4- to8-membered carbocycle or heterocycle which may additionally be fusedwith one, two or three cycloalkyl, heterocycloalkyl, aryl or hetarylgroups, where the heterocycle and, if present, the fused-on groups mayeach bear, independently of one another, one, two, three or foursubstituents selected from among alkyl, cycloalkyl, heterocycloalkyl,aryl, hetaryl, COOR^(f), COO⁻M⁺, SO₃R^(f), SO⁻ ₃M⁺, NE⁴E⁵,alkylene-NE⁴E⁵, NE⁴E⁵E⁶⁺X⁻, alkylene-NE⁴E⁵E⁶⁺X⁻, OR^(f), SR^(f),(CHR^(e)CH₂O)_(y)R^(f), (CH₂N(E⁴))_(y)R^(f), (CH₂CH₂N(E⁴))_(y)R^(f),halogen, trifluoromethyl, nitro, acyl and cyano, where R^(f), E⁴, E⁵ andE⁶ are identical or different radicals selected from among hydrogen,alkyl, cycloalkyl and aryl, R^(e) is hydrogen, methyl or ethyl, M⁺ is acation, is an anion and y is an integer from 1 to
 240. 12. A processaccording to claim 2 further comprising removing at least part of theby-products from the catalytically active fluid prior to recirculatingthe fluid.
 13. A process according to claim 5, wherein the molar ratiois from 0.1:1 to 1.5:1.
 14. A process according to claim 9, wherein R¹,R², R⁴ and R⁵ are selected independently from among groups of theformulae III.a to III.k

where Alk is a C₁-C₁₂-alkyl group and R^(a), R^(b), R^(c) and R^(d) areeach, independently of one another, hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy,acyl, halogen, C₁-C₄-alkoxycarbonyl or carboxyl.
 15. A process accordingto claim 9, wherein the bridging group Y is selected from among groupsof the formulae IV.a to IV.u

where R^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV),R^(IV′), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), R^(XI) andR^(XII) are each, independently of one another, hydrogen, alkyl,cycloalkyl, heterocycloalkyl, aryl, hetaryl, hydroxy, thiol,polyalkylene oxide, polyalkylenimine, alkoxy, halogen, SO₃H, sulfonate,NE¹E², alkylene-NE¹E², nitro, alkoxycarbonyl, carboxyl, acyl or cyano,where E¹ and E² are identical or different radicals selected from amonghydrogen, alkyl, cycloalkyl and aryl, Z is O, S, NR^(δ) or SiR^(δ)R^(ε),where R^(δ) and R^(ε) are each, independently of one another, hydrogen,alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl, or Z is aC₁-C₄-alkylene bridge which may have a double bond and/or bear an alkyl,cycloalkyl, heterocycloalkyl, aryl or hetaryl substituent, or Z is aC₂-C₄-alkylene bridge which is interrupted by O, S or NR^(δ) orSiR^(δ)R^(ε), where, in the groups of the formulae IV.a and IV.b, twoadjacent radicals R^(I)to R^(VI) together with the carbon atoms of thebenzene ring to which they are bound may also form a fused ring systemhaving 1, 2 or 3 further rings, where, in the groups of the formulaeIV.h to IV.n, two geminal radicals R^(I), R^(I′); R^(II), R^(II′);R^(III), R^(III′) and/or R^(IV), R^(IV″) may also represent oxo or aketal thereof, A¹ and A² are each, independently of one another, O, S,SiR^(φ)R^(γ), NR^(η) or CR^(ι)R^(κ), where R^(φ), R^(γ), R^(η), R^(ι)and R^(κ) are each, independently of one another, hydrogen, alkyl,cycloalkyl, heterocycloalkyl, aryl or hetaryl, A³ and A⁴ are each,independently of one another, SiR, N or CR^(ι), D is a divalent bridginggroup of the formula

where R⁹, R^(9′), R¹⁰ and R^(10′) are each, independently of oneanother, hydrogen, alkyl, cycloalkyl, aryl, halogen, trifluoromethyl,carboxyl, carboxylate or cyano, where R^(9′) together with R^(10′) canalso represent the second bond of a double bond between the two carbonatoms to which R^(9′) and R^(10′) are bound, and/or R⁹ and R¹⁰ togetherwith the carbon atoms to which they are bound may also form a 4- to8-membered carbocycle or heterocycle which may additionally be ffsedwith one, two or three cycloalkyl, heterocycloalkyl, aryl or hetarylgroups, where the heterocycle and, if present, the fused-on groups mayeach bear, independently of one another, one, two, three or foursubstituents selected from among alkyl, cycloalkyl, heterocycloalkyl,aryl, hetaryl, COOR^(f), COO⁻M⁺, SO₃R^(f), SO⁻ ₃M⁺, NE⁴E⁵,alkylene-NE⁴E⁵, NE⁴E⁵E⁶⁺X⁻, alkylene-NE⁴E⁵E⁶⁺X⁻, OR^(f), SR^(f),(CHR^(e)CH₂O)_(y)R^(f), (CH₂N(E⁴))_(y)R^(f), (CH₂CH₂N(E⁴))_(y)R^(f),halogen, trifluoromethyl, nitro, acyl and cyano, where R^(f), E⁴, E⁵ andE⁶ are identical or different radicals selected from among hydrogen,alkyl, cycloalkyl and aryl, R^(e) is hydrogen, methyl or ethyl, M⁺ is acation, is an anion and y is an integer from 1 to
 240. 16. A processaccording to claim 10, wherein the bridging group Y is selected fromamong groups of the formulae IV.a to IV.u

where R^(I), R^(I′), R^(II), R^(II′), R^(III), R^(III′), R^(IV),R^(IV′), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), R^(XI) andR^(XII) are each, independently of one another, hydrogen, alkyl,cycloalkyl, heterocycloalkyl, aryl, hetaryl, hydroxy, thiol,polyalkylene oxide, polyalkylenimine, alkoxy, halogen, SO₃H, sulfonate,NE¹E², alkylene-NE¹E², nitro, alkoxycarbonyl, carboxyl, acyl or cyano,where E¹ and E² are identical or different radicals selected from amonghydrogen, alkyl, cycloalkyl and aryl, Z is O, S, NR^(δ) or SiR^(δ)R^(ε),where R^(δ) and R^(ε) are each, independently of one another, hydrogen,alkyl, cycloalkyl, heterocycloalkyl, aryl or hetaryl, or Z is aC₁-C₄-alkylene bridge which may have a double bond and/or bear an alkyl,cycloalkyl, heterocycloalkyl, aryl or hetaryl substituent, or Z is aC₂-C₄-alkylene bridge which is interrupted by O, S or NR^(δ) orSiR^(δ)R^(ε), where, in the groups of the formulae IV.a and IV.b, twoadjacent radicals R^(I)to R^(VI) together with the carbon atoms of thebenzene ring to which they are bound may also form a fused ring systemhaving 1, 2 or 3 further rings, where, in the groups of the formulaeIV.h to IV.n, two geminal radicals R^(I), R^(I′); R^(II), R^(II′);R^(III), R^(III′) and/or R^(IV), R^(IV″) may also represent oxo or aketal thereof, A¹ and A² are each, independently of one another, O, S,SiR^(φ)R^(γ), NR^(η) or CR^(ι)R^(κ), where R^(φ), R^(γ), R^(η), R^(ι)and R^(κ) are each, independently of one another, hydrogen, alkyl,cycloalkyl, heterocycloalkyl, aryl or hetaryl, A³ and A⁴ are each,independently of one another, SiR, N or CR^(ι), D is a divalent bridginggroup of the formula

where R⁹, R^(9′), R¹⁰ and R^(10′) are each, independently of oneanother, hydrogen, alkyl, cycloalkyl, aryl, halogen, trifluoromethyl,carboxyl, carboxylate or cyano, where R^(9′) together with R^(10′) canalso represent the second bond of a double bond between the two carbonatoms to which R^(9′) and R^(10′) are bound, and/or R⁹ and R¹⁰ togetherwith the carbon atoms to which they are bound may also form a 4- to8-membered carbocycle or heterocycle which may additionally be fusedwith one, two or three cycloalkyl, heterocycloalkyl, aryl or hetarylgroups, where the heterocycle and, if present, the fuised-on groups mayeach bear, independently of one another, one, two, three or foursubstituents selected from among alkyl, cycloalkyl, heterocycloalkyl,aryl, hetaryl, COOR^(f), COO⁻M⁺, SO₃R^(f), SO⁻ ₃M⁺, NE⁴E⁵,alkylene-NE⁴E⁵, NE⁴E⁵E⁶⁺X⁻, alkylene-NE⁴E⁵E⁶⁺X⁻, OR^(f), SR^(f),(CHR^(e)CH₂O)_(y)R^(f), (CH₂N(E⁴))_(y)R^(f), (CH₂CH₂N(E⁴))_(y)R^(f),halogen, trifluoromethyl, nitro, acyl and cyano, where R^(f), E⁴, E⁵ andE⁶ are identical or different radicals selected from among hydrogen,alkyl, cycloalkyl and aryl, R^(e) is hydrogen, methyl or ethyl, M⁺ is acation, is an anion and y is an integer from 1 to
 240. 17. A process forthe hydroformylation of compounds which comprises, providing at leastone compound with an ethylenically unsaturated double bond and reactingthe at least one compound with carbon monoxide and hydrogen in at leastone reaction zone in the presence of a catalytically active fluid whichcomprises a dissolved metal complex of a metal of transition group VIIIof the Periodic Table of the Elements with at least one phosphoramiditecompound as ligand, wherein the fluid is brought into contact with atleast one base selected from trialkyl amines, dialkyaryl amines,alkyldiaryl amines, and triaryl amines, and wherein the phosphoramiditecompound is selected from among compounds of the formulae I and II

where R¹ and R⁵ are each, independently of one another, pyrrole groupsbound via the nitrogen atom to the phosphorus atom, R², R³ and R⁴ areeach, independently of one another, alkyl, cycloalkyl, heterocycloalkyl,aryl or hetaryl, or R¹ together with R² and/or R⁴ together with R⁵ formsa divalent group containing at least one pyrrole group bound via thepyrrolic nitrogen atom to the phosphorus atom, Y is a divalent bridgedgroup having from 2 to 20 bridge atoms between the flanking bonds, X¹,X², X³ and X⁴ are selected independently from among O, S,SiR^(α)R^(β)and NR^(γ), where R^(α), R^(β)and R^(γ)are each,independently of one another, hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl or hetaryl, and a, b, c and d are each,independently of one another, 0 or 1, further comprising removing fromthe reaction zone a product mixture which is subjected to afractionation to give a fraction consisting essentially of ahydroformylation product and a fraction comprising the catalyticallyactive fluid in which the by-products of the hydroformylation which haveboiling points higher than that of the hydroformylation product arepresent and the metal complex is dissolved, and recirculating thecatalytically active fluid to the reaction zone.
 18. The processaccording to claim 17, wherein the recirculating of the catalyticallyactive fluid is carried out in the absence of carbon monoxide andhydrogen.
 19. A method of stabilizing a catalytically active fluidcomprising a dissolved metal complex of a metal of transition group VIIIof the Periodic Table of the Elements with at least one phosphoramiditecompound as ligand in the hydroformylation of ethylenically unsaturatedcompounds, which comprises bringing the fluid into contact with at leastone base selected from trialkyl amines, dialkyaryl amines, alkyldiarylamines, triaryl amines, and bases immobilized on a solid phase, or acombination thereof, wherein the at least one phosphoramidite compoundis selected from among compounds of the formulae I and II

where R¹ and R⁵ are each, independently of one another, pyrrole groupsbound via the nitrogen atom to the phosphorus atom, R², R³ and R⁴ areeach, independently of one another, alkyl, cycloalkyl, heterocycloalkyl,aryl or hetaryl, or R¹ together with R² and/or R⁴ together with R⁵ formsa divalent group containing at least one pyrrole group bound via thepyrrolic nitrogen atom to the phosphorus atom, Y is a divalent bridgedgroup having from 2 to 20 bridge atoms between the flanking bonds, X¹,X², X³ and X⁴ are selected independently from among O, S,SiR^(α)R^(β)and NR^(γ), where R^(α), R^(β)and R^(γ)are each,independently of one another, hydrogen, alkyl, cycloalkyl,heterocycloalkyl, aryl or hetaryl, and a, b, c and d are each,independently of one another, 0 or
 1. 20. A method according to claim19, wherein base is soluble in the catalytically active fluid and/or thefluid is brought into contact with a base immobilized on a solid phase.